U.S. patent number 5,755,104 [Application Number 08/583,138] was granted by the patent office on 1998-05-26 for heating and cooling systems incorporating thermal storage, and defrost cycles for same.
This patent grant is currently assigned to Store Heat and Produce Energy, Inc.. Invention is credited to Matthew D. Emmert, Oleg Mankovskiy, Alexander P. Rafalovich.
United States Patent |
5,755,104 |
Rafalovich , et al. |
May 26, 1998 |
**Please see images for:
( Certificate of Correction ) ** |
Heating and cooling systems incorporating thermal storage, and
defrost cycles for same
Abstract
An apparatus for heating or cooling a space comprises a main
flow loop including a compressor (1012), an outside heat exchanger
(1014), an inside heat exchanger (1016) connected to allow working
fluid to circulate therebetween, and a first valve (1026) between
the outside heat exchanger (1014) and the inside heat exchanger
(1016) selectively to block flow between the outside heat exchanger
(1014) and the inside heat exchanger (1016). A first bypass line
extends between the outlet of the outside heat (1014) and the inlet
of the inside heat exchanger (1016). A thermal storage device
(1018) is positioned in the first bypass line. A second bypass line
extends between the inlet of the inside heat exchanger (1016) and
the outlet of the inside heat exchanger (1016) and communicates
with the first bypass line to bypass the inside heat exchanger
(1016). A second valve (1030) is positioned in the second bypass
line to block flow through the second bypass line selectively. Also
described is a method for operating a refrigeration system in a hot
gas defrost mode, wherein negative thermal potential transferred to
the refrigerant from the frosted evaporator is captured and stored
in a thermal storage device for later use. In addition, described
is a method for operating a refrigeration system in a
low-temperature condensing cycle.
Inventors: |
Rafalovich; Alexander P.
(Indianapolis, IN), Emmert; Matthew D. (Fishers, IN),
Mankovskiy; Oleg (Indianapolis, IN) |
Assignee: |
Store Heat and Produce Energy,
Inc. (Indianapolis, IN)
|
Family
ID: |
24331830 |
Appl.
No.: |
08/583,138 |
Filed: |
December 28, 1995 |
Current U.S.
Class: |
62/81; 62/205;
62/278 |
Current CPC
Class: |
F25B
13/00 (20130101); F25B 47/022 (20130101); F25D
16/00 (20130101); F25B 2400/04 (20130101); F25B
2400/075 (20130101); F25B 2400/24 (20130101) |
Current International
Class: |
F25D
16/00 (20060101); F25B 47/02 (20060101); F25B
13/00 (20060101); F25B 047/02 () |
Field of
Search: |
;62/81,160,151,196.4,197,198,205,238.6,238.7,278,277,201
;165/10,1A,902 ;237/2B |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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188987 |
|
Nov 1982 |
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JP |
|
060187 |
|
Apr 1984 |
|
JP |
|
009560 |
|
Mar 1986 |
|
JP |
|
243284 |
|
Oct 1986 |
|
JP |
|
Other References
Electro Hydronic Systems, Water Source Heat Pump Design Manual,
(Apr. 1987) S.E.D. 13002. .
York Applied Systems, IceBalls.TM. Thermal Storage System, 1990.
.
Cristopia Energy Systems, STL Thermal Energy Storage Manual, 1990.
.
Fath, Hassan E.S., Heat Exchanger Performance For Latent Heat
Thermal Energy Storage System, 1991. .
Gultekin, Nurbay et al.,Heat Storage Chemical Materials Which Can
Be Used For Domesti Heating By Heat Pumps, 1991. .
Sozen, Zeiki Z. et al., Thermal Energy Storage By Agitated Capsules
of Phase Change, 1988. .
Havelsky, V. et al., Heat Pump Design With Thermal Storage, Heat
Recovery Systems and CHP, vol. 9, No. 5, pp. 447-450, 1989. .
Reardon, J. Gregory, Heating with Ice Storage--A Case Study, 1990.
.
Adams, Laura S., Lennox Cool Thermal Energy Storage (CTES) A Direct
Expansion Storage Module For Split System Air Conditioners, 1990.
.
Shive, Patrick L., An Electric Heat Pump With an Off-Peak Electric
Hydronic Based Backup System, 1990. .
Uhr, Jr., C. William A "Smart" Triple Function Storage System,
1990. .
Best, Gerald, Phenix THP/3 Systems: Projected Utility Value, 1990.
.
Courtright, Henry A. et al., Off-Peak Space Heating Systems, 1990.
.
Powell Energy Products, Inc. Brochure, Introducing Ice.
Storage.Air-Conditioning To The Utility, 1990..
|
Primary Examiner: Tanner; Harry B.
Attorney, Agent or Firm: Woodard, Emhardt, Naughton Moriarty
& McNett
Claims
What is claimed is:
1. A method for operating a refrigeration system having a defrost
cycle, the system including a condenser, a first metering device, a
first bypass line for selectively bypassing the first metering
device, a thermal storage device including a thermal storage
medium, a second metering device, an evaporator, a second bypass
line for selectively bypassing the second metering device and
evaporator, a compressor, a refrigerant, a third bypass line for
selectively directing hot refrigerant exiting the compressor to the
evaporator and a fourth bypass line for selectively directing
refrigerant liquefied in the evaporator to the first metering
device and further through the thermal storage device and the
second bypass line to the compressor, the method including the
steps of:
(a) charging the thermal storage device by:
(i) desuperheating and condensing refrigerant from a vapor to a
liquid in the condenser after the refrigerant is compressed;
(ii) flowing the liquid refrigerant through the first metering
device;
(iii) evaporating the refrigerant in the thermal storage device and
transferring negative thermal potential to the thermal storage
medium from the refrigerant;
(iv) flowing refrigerant vapor through the second bypass line to
the compressor; and
(v) compressing the refrigerant vapor in the compressor;
(b) discharging the thermal storage device by:
(i) desuperheating and condensing refrigerant vapor in the
condenser after the refrigerant is compressed;
(ii) flowing the refrigerant through the first bypass line;
(iii) extracting heat from the refrigerant in the thermal storage
device;
(iv) flowing liquid refrigerant through the second metering
device;
(v) evaporating the refrigerant in the evaporator; and
(vi) compressing the refrigerant vapor in the compressor; and
(c) defrosting the evaporator by:
(i) desuperheating and condensing refrigerant directed by the third
bypass line to the evaporator from vapor to liquid in the
evaporator after the refrigerant is compressed;
(ii) flowing the liquid refrigerant through the fourth bypass line
to the first metering device;
(iii) evaporating the refrigerant in the thermal storage device and
simultaneously extracting heat from the refrigerant to the thermal
storage medium;
(iv) flowing refrigerant vapor through the second bypass line to
the compressor; and
(v) compressing the refrigerant vapor in the compressor.
2. A method for operating a refrigeration system in a cycle with
low-temperature condensing, the system including a refrigerant and
a refrigerant circuit including a compressor, a condenser, a first
metering device having a setting for supercooling, a
low-temperature condensing device, a second metering device set for
superheating, and an evaporator, the method comprising the steps
of:
compressing refrigerant vapor in the compressor;
after said compressing, condensing the refrigerant vapor to liquid
in the condenser;
after said condensing, expanding the refrigerant in the first
metering device set for supercooling to form a vaporized portion of
refrigerant;
after said expanding, low-temperature condensing the vaporized
portion of refrigerant in the low-temperature condenser;
after said low-temperature condensing, flowing the refrigerant
through the second metering device set for superheating to expand
the refrigerant;
after said flowing, evaporating refrigerant remaining in liquid
form to vapor in the evaporator; and
after said evaporating, compressing the refrigerant vapor in the
compressor.
3. The method of claim 2, wherein said low-temperature condenser is
a thermal storage device.
4. The method of claim 3, also including the steps of:
defrosting the evaporator with compressed refrigerant vapor from
the compressor, wherein negative thermal potential is transferred
to the refrigerant vapor which is at least partially condensed to
liquid;
after said defrosting, expanding the refrigerant in a metering
device;
after said expanding, transferring negative thermal potential from
the refrigerant to the thermal storage device, wherein the
refrigerant is evaporated to vapor; and
after said transferring, compressing the refrigerant vapor in the
compressor.
5. A system for operating a refrigeration cycle in a cycle with
low-temperature condensing, comprising:
a refrigerant and a refrigerant circuit;
said refrigerant circuit including:
a compressor for compressing the refrigerant;
a condenser for condensing refrigerant exiting the compressor;
a supercooling metering device having a setting for supercooling
for expanding refrigerant exiting the condenser;
a low-temperature condensing device for condensing refrigerant
vapor exiting said supercooling metering device; and
a superheating metering device set for superheating for further
expanding refrigerant exiting said low-temperature condensing
device.
6. The system of claim 5 wherein said low-temperature condensing
device is a thermal storage device.
7. A method for operating a refrigeration system in a
low-temperature condensing mode, the system including a refrigerant
and a refrigerant circuit including a compressor, a condenser, a
first metering device having a setting for supercooling, a thermal
storage device, including a refrigeration coil and a thermal
storage medium, an evaporator, a bypass line for bypassing the
evaporator, a second metering device set for superheating, and a
third metering device set for superheating, the method comprising
the steps of:
charging the thermal storage device by
a) desuperheating and condensing refrigerant from a vapor to a
liquid in the condenser after the refrigerant is compressed;
b) flowing the liquid refrigerant through the second metering
device;
c) evaporating the refrigerant in the refrigeration coil of the
thermal storage device and transferring negative thermal potential
to the thermal storage medium from the refrigerant;
d) flowing refrigerant vapor through the bypass line to the
compressor; and
e) compressing the refrigerant vapor in the compressor discharging
the thermal storage device by
a) desuperheating and condensing refrigerant vapor in the condenser
after the refrigerant is compressed;
b) flowing the refrigerant through the first metering device set
for supercooling;
c) re-condensing refrigerant by transferring thermal potential from
the refrigerant to the charged thermal storage medium at a
temperature level close to the temperature of the charged thermal
storage medium;
d) flowing liquid refrigerant after the thermal storage device
through the third metering device;
e) evaporating the refrigerant in the evaporator; and
f) compressing the refrigerant vapor in the compressor.
Description
BACKGROUND
The present invention relates to heating and cooling systems
incorporating thermal storage devices. More particularly, the
present invention relates to various refrigerant-based heating and
cooling systems incorporating direct expansion thermal storage
devices, and to methods for defrosting expansion devices of such
systems.
As further background, air source heat pumps extract heat from
outdoor air and deliver it to the air distribution system of an
indoor space to be heated. In effect, air source heat pumps "pump"
heat into a space just as typical air conditioners "pump" heat out
of a space.
However, when ambient temperatures fall below a certain limiting
level, heat pump efficiency decreases dramatically. That is, a
balance point temperature may be defined for heat pump systems at
which the heat pump capacity equals the heat loss from the home.
Supplemental heating will be required to maintain temperatures in
the heated space when the ambient temperature falls below the
balance point.
Unfortunately, the balance point for most heat pump systems ranges
from about 20.degree. F. to about 32.degree. F. (about -7.degree.
C. to about 0.degree. C.). Thus, heat pumps operating in typical
North American wintertime conditions normally must be provided with
supplemental heating. In addition, heat pumps are often called upon
to operate under rapidly changing ambient conditions which may give
rise to a mismatch between heat pump heat production capability and
heat demand. For example, in operation during a typical winter day,
average ambient temperatures may well remain close to the system
balance point temperature during the daytime, but may rapidly fall
well below the system balance point temperature at night. Thus, the
system is likely to operate with excess heating capacity during the
daytime and inadequate heating capacity at nighttime. Supplemental
heating will likely be required at nighttime.
An analogous phenomenon occurs when the heat pump system is
operating in a cooling mode to extract heat from the conditioned
space. The efficiency of the heat pump decreases as ambient
temperature increases. In typical summertime operation, the heat
pump may operate with adequate cooling capacity during daytime
hours but will have excess cooling capacity during nighttime
hours.
The requirement for supplemental heating reduces any economic
benefit that a heat pump system might otherwise provide over
conventional heating systems. Moreover, such a system will most
probably be operating at highest capacity (and lowest efficiency)
during on-peak billing hours (for example, during the daytime
generally).
Some researchers have attempted to overcome these problems by
incorporating a thermal storage device into the heat pump system.
See, for example, U.S. Pat. Nos. 4,100,092; 4,256,475; 4,693, 089;
4,739,624; and 4,893,476. Such devices typically use a phase change
material to enable thermal energy storage in the form of latent
heat as the material changes phase, typically between solid and
liquid. The thermal energy storage device would, for example, store
the excess heating capacity during daytime winter operation for
release during nighttime operation when supplemental heating would
otherwise be needed. Analogously, the thermal energy device would
store "coolness" during nighttime summer operation and would
release the "coolness" during daytime operation, reducing the
system power requirements.
Typically, heat pump and air conditioning systems incorporating
thermal storage devices have sought to achieve energy savings by
reducing the load on the system compressor, or by shifting
electrical use patterns by "decoupling" compressor operation from
building loads, as in the case of so-called "refrigeration coupled
thermal energy storage" systems. Some systems, in fact, are
designed to interrupt operation of the compressor altogether at
certain times, thereby reducing the overall compressor energy
consumption. However, such systems require a supplemental fan to
achieve heat transfer directly from the thermal storage medium.
Other such systems rely upon existing fans but require substantial
additional ductwork to deliver air flow from the fans to the
thermal storage device.
In addition, attempts have been made to provide a thermal storage
device to provide heat transfer between a working fluid and phase
change materials contained in the thermal storage device.
Researchers have attempted to encapsulate phase change materials in
an effort to maximize surface area available for heat transfer
contact with the working fluid. In addition, researchers have
developed a variety of phase change compositions suitable for use
over various temperature ranges, increasing system flexibility.
Examples of designs of thermal storage devices are numerous in the
art. See, for example, U.S. Pat. Nos. 3,960,207; 4,127,161;
4,29,072; 4,256,475; 4,283,925; 4,332,290; 4,609,036; 4,709,750;
4,753,080; 4,807,696; 4,924,935; and 5,000,252.
Further, researchers have proposed a variety of control strategies
for enhancing operating efficiency of heat pump systems
incorporating thermal storage devices. Such control strategies, for
example, may involve continuous computation of thermal storage
target conditions based upon time, ambient conditions, and/or
conditions in the thermal storage device. See, for example, U.S.
Pat. Nos. 4,645,908; 4,685,307; and 4,940,079.
Other attempts were made to incorporate a thermal storage device in
the refrigeration cycle to shift energy consumption and to increase
efficiency when the thermal storage presumably works as a
subcooler. See, for example U.S. Pat. No. 5,386,709. The thermal
storage subcooler is located immediately after a condenser or there
is a receiver between the thermal storage and the condenser.
Disadvantages of this design may be appreciated upon reviewing
FIGS. 22 and 23. The desired functional scenario for such
subcooling is illustrated by following compressing refrigerant line
1-2', condensing refrigerant line 2'-3', subcooling line 3'-3,
expanding line 3-4, and evaporating line 4-1 (FIG. 22). In reality,
because of the existence of the low temperature potential and a big
heat transfer coil in the thermal storage device, condensing occurs
in the thermal storage, so the refrigeration cycle follows
compression to lower pressure line 1-2, condensing refrigerant in
the thermal storage line 2-3, expanding line 3-4, and evaporating
line 4-1. Compared to the previously described cycle 1-2'-3'-3-4-1,
here energy of the thermal storage device is spent not only for
subcooling but also for condensing. Thus, the thermal storage
charged by the same cooling capacity will provide the cycle
1-2-3-4-1 by negative thermal potential just a portion of the time
it provides cycle 1-2'-3'-3-4-1. In addition, there is another
scenario of the cycle with the thermal storage according to U.S.
Pat. No. 5,386,709: compressing line 1-2, partly condensing in the
conventional condenser line 2-2', additional condensing and
subcooling in the thermal storage line 2'-3'-3, expanding line 3-4,
and evaporating line 4-1 (FIG. 23).
Several experiments conducted by the inventors have shown that an
equally charged thermal storage installed according to U.S. Pat.
No. 5,386,709 runs out of cooling capacity two to three times
faster than in the cycle 1-2'-3'-3-4-1 (FIG. 22). Thus, systems
such as those described in U.S. Pat. No. 5,386,709 present several
disadvantages.
Another challenge encountered by researchers attempting to optimize
energy consumption in heating and cooling apparatuses is the need
to quickly and efficiently defrost evaporator devices which have
drawn heat from their surrounding environment. In previous work,
defrosting cycles have involved primarily two operational modes:
resistive heat and the "hot gas" method. Resistive heat utilizes a
heating element attached or adjacent to the evaporator, and is
generally energy-intensive. In the "hot gas" method, the
heating/cooling cycle is reversed and high-pressure, gaseous
refrigerant from the compressor is routed to the frost-laden
evaporator, which in this reversed cycle acts as a condenser. The
resulting heat transfer melts the ice on the exterior of the
refrigerator. Many such systems are known and are illustrated in
U.S. Pat. Nos. 5,319,940; 5,315,836; 5,275,008; 5,167,130;
5,157,935; 4,197,716; 5,150,582; and 5,138,843.
Attempts have also been made to incorporate energy-efficient
defrost cycles into heating and cooling systems also including
thermal storage devices. For example, U.S. Pat. No. 5,269,151
describes a refrigeration system with a "passive" defrost system.
During normal operation of the system, waste heat from the liquid
refrigerant line between the outlet of the condenser and a
downstream thermal expansion device is collected in a thermal
storage device. Upon shut-down of the compressor, a passive defrost
cycle is initiated in which a gravity heat pipe is used to deliver
the stored heat to the evaporator to defrost the same.
These attempts, while numerous, have not heretofore resulted in the
widespread adoption of thermal storage devices for use in
connection with refrigeration and heat pump systems. A need exists
for refrigeration and heat pump systems which can be readily
retrofit in existing heat pump systems and which provide a variety
of configurations for controlling flow of the working fluid (for
example, refrigerant) in a circuit designed to maximize system
efficiency and flexibility.
Furthermore, a need exists to provide a conditioning system which
can be operated in both a conventional cycle and a thermal storage
charging and discharging cycle to provide greater flexibility in
selection of compressors. In air conditioning particularly, there
is a need to provide systems which can rapidly cool down a space
during peak demand period, but which avoids reliance on excess
cooling capacity (i.e., cooling capacity which goes unused during
off-peak demand periods).
Moreover, additional needs exist to provide heating and cooling
system reliability, and energy-efficient ways to defrost
evaporators used in such heating and cooling systems.
According to one embodiment of the present invention, a heat pump
and air conditioning system is provided. The system is operable in
at least one of a heating mode and a cooling mode, both modes
including a thermal charging cycle and a thermal discharging cycle.
The system comprises a refrigerant circuit including a compressor
and, in serial connection, a first heat exchanger, an expansion
device, and a second heat exchanger. The system further comprises a
thermal storage device, first means for connecting the thermal
storage device in parallel with the first heat exchanger, a first
pair of three-way valves positioned to block flow to and from the
first connecting means, second means for connecting the thermal
storage device in parallel with the second heat exchanger, and a
second pair of threeway valves positioned to block flow to and from
the second connecting means. The system further comprises means for
controlling the first and second pairs of three-way valves so that
during operation in the heating mode, charging cycle, refrigerant
from the refrigerant circuit flows in the first connecting means
through the thermal storage device, and during operation in the
cooling mode, discharging cycle, refrigerant from the refrigerant
circuit flows in the second connecting means through the thermal
storage device.
In accordance with a further embodiment of the present invention, a
heat pump and air conditioning system is provided. The system is
operable in at least one of a heating and a cooling mode, both
modes including thermal charging and discharging cycles. The system
comprises a refrigerant circuit, a phase change heat exchanger or
thermal storage device positioned in the refrigerant circuit, a
pair of bypass conduits, and a controller for controlling flow
through the bypass conduits. The refrigerant circuit includes a
compressor, and, in serial connection, a first heat exchanger, a
first expansion device, a second expansion device, and a second
heat exchanger. The thermal storage device is positioned in the
refrigerant circuit between the first and second expansion devices.
The first bypass conduit bypasses the first expansion device, and
includes a first controlled valve, while the second bypass conduit
bypasses the second expansion device and includes a second
controlled valve. The means for controlling operation of the first
and second controlled valves operates so that during thermal
charging cycle, refrigerant flowing in the refrigerant circuit
bypasses the first expansion device and during the thermal
discharging cycle, refrigerant bypasses the second expansion
device.
In accordance with another aspect of the invention, the first
bypass line further bypasses the first heat exchanger and the
second bypass line further bypasses the second heat exchanger.
According to yet a further aspect of the invention, a heat pump and
air conditioning system operable in at least on of a heating and a
cooling mode comprises a refrigerant circuit including a
compressor, and, in serial connection, a first heat exchanger, a
four-way valve, and a second heat exchanger. The system further
includes a thermal storage circuit including a thermal storage
device, an expansion device, a first conduit extending between the
four-way valve and the expansion device, and a second conduit
extending between the four-way valve and the thermal storage
device. The system further includes means for controlling operation
of the four-way valve so that during operation in the heating mode,
charging cycle, and the cooling mode, discharging cycle,
refrigerant flowing in the refrigerant circuit flows through the
thermal storage device prior to passing through the expansion
device, a and during operation in the heating mode, discharging
cycle and the cooling mode, charging cycle, refrigerant flowing in
the refrigerant circuit flows through the expansion device before
flowing through the thermal storage device.
In accordance with yet another aspect of the invention, the system
further comprises a first bypass conduit extending between the
refrigerant circuit and the thermal storage circuit to bypass the
first heat exchanger and a second bypass conduit extending between
the refrigerant circuit and the thermal storage circuit to bypass
the second heat exchanger, and wherein the control means includes
first means for directing flow between the refrigerant circuit and
the first bypass conduit and second means for directing flow
between the refrigerant circuit and the second bypass conduit.
Further in accordance with the present invention, a method is
provided for conditioning a space using a heat pump and air
conditioning system the system includes a refrigerant circuit and a
thermal storage device and the refrigerant circuit includes a
compressor, a four-way reversing valve, and, in a serial
connection, a first heat exchanger, an expansion device, and a
second heat exchanger. The thermal storage device is connected in
parallel with both the first and second heat exchangers. The method
comprises splitting refrigerant flow from the compressor into a
first and a second portion, simultaneously flowing the first
portion through the first heat exchanger and the second portion
through the thermal storage device.
Advantageously, systems of the present invention regulate
refrigerant flow through the first and second heat exchangers to
achieve energy savings. In the present systems, in contrast to
those of the prior art, compressor operation in continuous. Systems
of the present invention therefore avoid the need for supplemental
fans directed through the phase change storage medium or
supplemental ductwork from existing fans. Thus, systems of the
present invention are easier to retrofit with existing heat pump
systems currently operating in many settings without the benefit of
thermal storage capability. Moreover, systems of the present
invention may have higher efficiency in the heating mode as
compared to conventional systems due to the reliance on thermal
storage. Indeed, systems of the present invention require
compressors having smaller compressor ratios than those commonly
used in conventional systems, such that reliance on the present
systems may allow a single stage compressor to be substituted for a
two-stage compressor.
In addition, systems of the present invention rely upon a single
refrigerant circuit (including a single compressor) for operation
in both heating and cooling modes. Furthermore, no supplemental
phase change material for cool storage is necessary with systems of
the present invention.
In accordance with yet a further aspect of the invention, the phase
change heat exchanger or thermal storage device includes a
container defining an interior region configured to receive a first
phase change material therein, the first phase change material
having a first melt temperature. The thermal storage device further
includes at least one refrigerant coil extending through the
interior region to deliver a flow of refrigerant therethrough. The
device also includes a plurality of phase change capsules disposed
in the interior region, the phase change capsules each containing a
second phase change material having a second melt temperature
higher than the first melt temperature.
In accordance with yet a further aspect of the present invention,
an apparatus is provided for heating or cooling a space. The
apparatus comprises a main flow loop, a bypass line, a thermal
storage device positioned in the bypass line, and a working fluid
pump. The main flow loop includes a compressor, an outside heat
exchanger, and inside heat exchanger, and a first valve located
between the outside heat exchanger. The bypass line extends between
the outlet of the outside heat exchanger and the outlet of the
inside heat exchanger such that working fluid flowing in the bypass
line bypasses the inside heat exchanger. The working fluid pump is
positioned between the thermal storage device and the inlet side of
the inside heat exchanger. The working fluid pump advantageously
enables working fluid to circulate between the inside heat
exchanger and the thermal storage device in the bypass line
independently of the circulation of working fluid in the main flow
loop.
In accordance with yet a further aspect of the present invention,
an apparatus for heating or cooling a space comprises a main flow
loop including a compressor, an outside heat exchanger, an inside
heat exchanger, and a first valve selectively blocking flow between
the outside and inside heat exchangers. The apparatus also includes
a first bypass line, a thermal storage device positioned in the
first bypass line, a second bypass line, and a second valve
positioned in the second bypass line to selectively block flow
therethrough. The first bypass line extends between the outlet of
the outside heat exchanger and the inlet of the inside heat
exchanger. The second bypass line extends between the inlet of the
inside heat exchanger and the outlet of the inside heat exchanger
and communicates with the first bypass line, advantageously
allowing working fluid to flow from the outside heat exchanger
through both the first and second bypass lines to the compressor,
bypassing the inside heat exchanger.
In accordance with a further embodiment of the present invention, a
method is provided for discharging stored energy from a thermal
storage device to heat or cool a space using a heating or cooling
system. The system includes outside and inside heat exchangers, a
compressor, and a working fluid pump. The method comprises the
steps of initiating the flow of working fluid between the thermal
storage device and the inside heat exchanger using the working
fluid pump and condensing working fluid in the thermal storage
device and evaporating working fluid in the inside heat exchanger,
thereby cooling the space. The method further comprises the steps
of initiating flow of refrigerant between the outside heat
exchanger and the inside heat exchanger using the compressor, while
maintaining the flow of working fluid between the thermal storage
device and the inside heat exchanger, and condensing the working
fluid and the outside heat exchanger and evaporating working fluid
in the inside heat exchanger, thereby further cooling the
space.
In accordance with yet another aspect of the invention, a method is
provided for operating a refrigeration system in a defrost cycle,
the system including a refrigerant and a defrost loop including a
compressor, a frosted evaporator, a condenser, a metering device,
and a thermal storage device. The method includes defrosting the
frosted evaporator with compressed refrigerant vapor from the
compressor, wherein negative thermal potential is transferred to
the refrigerant vapor which is condensed to liquid. Thereafter, the
refrigerant is expanded in the metering device, and then negative
thermal potential is transferred from the refrigerant to the
thermal storage device, wherein the refrigerant is evaporated to
vapor. The refrigerant is then compressed in the compressor,
whereafter this series of steps can be repeated as necessary to
achieve defrost of the evaporator. In a more preferred mode, the
system includes a condenser, a first metering device, a first
bypass line for selectively bypassing the first metering device, a
thermal storage device including a thermal storage medium, a second
metering device, an evaporator, a second bypass line for
selectively bypassing the second metering device and evaporator, a
compressor, a refrigerant, a third bypass line for selectively
directing hot refrigerant exiting the compressor to the evaporator
and a fourth bypass line for selectively directing refrigerant
liquefied in the evaporator to the first metering device and
further through the thermal storage device and the second bypass
line to the compressor. The method includes the steps of:
(a) charging the thermal storage device by:
(i) desuperheating and condensing refrigerant from a vapor to a
liquid in the outside heat exchanger after the refrigerant is
compressed;
(ii) flowing the liquid refrigerant through the first metering
device;
(iii) evaporating the refrigerant in the thermal storage device and
transferring negative thermal potential to the thermal storage
medium from the refrigerant;
(iv) flowing refrigerant vapor through the second bypass line to
the compressor; and
(v) compressing the refrigerant vapor in the compressor;
(b) discharging the thermal storage device by:
(i) desuperheating and condensing refrigerant vapor in the outside
heat exchanger after the refrigerant is compressed;
(ii) flowing the refrigerant through the first bypass line;
(iii) extracting heat from the refrigerant in the thermal storage
device to subcool the refrigerant;
(iv) flowing liquid refrigerant through the second metering
device;
(v) evaporating the refrigerant in the inside heat exchanger;
and
(vi) compressing the refrigerant vapor in the compressor; and
(c) defrosting the inside heat exchanger by:
(i) desuperheating and condensing refrigerant directed by the third
bypass line to the inside heat exchanger from a vapor to liquid in
the inside heat exchanger after the refrigerant is compressed;
(ii) flowing the liquid refrigerant through the fourth bypass line
to the first metering device;
(iii) evaporating the refrigerant in the thermal storage device and
simultaneously extracting heat from the refrigerant to the thermal
storage medium;
(iv) flowing refrigerant vapor through the second bypass line to
the compressor; and
(v) compressing the refrigerant vapor in the compressor.
Another embodiment of the invention provides a novel method for
operating a refrigeration system in a low-temperature condensing
mode which provides an increase in overall system capacity. The
system includes a refrigerant and a refrigerant circuit including a
compressor, a condenser, and a metering device with a setting for
supercooling. For example, if the metering device is a thermostatic
expansion valve (TXV) with a temperature sensor installed after a
condenser, the negative setting of the sensor positions the TXV so
as to condense all refrigerant and to cool it to some definite
level. Also included is a metering device with a setting for
superheating. Again if the metering device is a TXV with a
temperature sensor installed after an evaporator, the positive
setting positions the TXV so as to evaporate all refrigerant and to
superheat it to some degree. The system also includes a low
temperature condenser, and an evaporator. The metering devices may
be separate devices or a single device with multiple settings, at
least one for supercooling and one for superheating. In accordance
with the invention, the method comprises compressing refrigerant
vapor in the compressor, and then condensing the refrigerant vapor
to liquid in the condenser. After condensing, the refrigerant is
passed through a metering device set for supercooling to expand the
liquid refrigerant (thus evaporating a portion of the refrigerant),
and then through a thermal storage or other device which acts as a
low temperature condenser, so as to condense that portion of the
refrigerant which was evaporated by the first metering device. The
refrigerant is then passed through a metering device set for
superheating to expand the refrigerant, and through an evaporator
to evaporate that portion of the refrigerant remaining in liquid
form. In this fashion, unlike existing refrigeration systems where
a thermal storage is located right after a condenser or after a
receiver and itself works at least partly as a condenser and only
partly as a subcooler, the metering device, which may be a TXV, an
orifice, a capillary tube or any pressure drop device between the
condenser and the thermal storage, forces refrigerant to condense
in the condenser, so the efficiency of the thermal storage is
increased and an advantageously high cooling capacity can be
realized from the system.
A still further embodiment of the invention provides a
refrigeration system operable in a low-temperature condensing mode.
The system includes a refrigerant and a refrigerant circuit
including a compressor for compressing the refrigerant, a condenser
for condensing refrigerant exiting the compressor, a supercooling
metering device having a setting for supercooling for expanding
refrigerant exiting the condenser, a low temperature condenser for
condensing refrigerant vapor exiting the supercooling metering
device, and a superheating metering device set for superheating for
further expanding refrigerant exiting the low-temperature
condensing device. The system is operable in a low-temperature
condensing mode as disclosed above, and provides high capacity. A
more preferred system configuration includes a main refrigeration
loop including a condenser, a supercooling metering device set for
supercooling connected to the condenser, and a supercooling
metering device set for superheating connected to the condenser.
The supercooling and superheating metering devices may be separate
metering devices, or in the case of TXV or the like may be a single
metering device having both supercooling and superheating settings,
and means for controlling the settings. A thermal storage device is
also provided in the main loop connected to and for receiving
refrigerant exiting the metering device(s), and for functioning as
a low temperature condenser. The main loop may also optionally
include one or more receivers for liquid refrigerant at appropriate
location(s), for example after the condenser and/or after the
thermal storage device. The main loop also includes a superheating
metering device and then an evaporator connected to and for
receiving refrigerant exiting the thermal storage device,
whereafter the refrigerant is again passed to the compressor. A
first bypass line is provided for selectively causing refrigerant
exiting the thermal storage device to selectively bypass the
evaporator and to be directed to the compressor. For these
purposes, a first valve is located in the main loop upstream of the
evaporator, and a second valve is located in the bypass line. With
the first valve open and the second valve closed, refrigerant flows
through the main loop, including the evaporator On the other hand,
with the first valve closed and the second valve open, refrigerant
bypasses the evaporator and flows through the bypass line.
Additional objects, features, and advantages of the invention will
become apparent to those skilled in the art upon consideration of
the following detailed description of preferred embodiments
exemplifying the best mode of carrying out the invention as
presently perceived.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic view of one embodiment of a heat pump and
air conditioning system in accordance with the present invention
showing a phase change heat exchanger or thermal storage device in
parallel connection with both a first and a second heat exchanger
and a control apparatus for controlling refrigerant flow
therebetween;
FIG. 2 is a diagrammatic view of another embodiment of a heat pump
and air conditioning system in accordance with the present
invention showing a thermal storage device in serial connection
with both a first and a second heat exchanger, bypass conduits for
bypassing both the first and the second heat exchangers along with
a first and a second expansion device, and a control apparatus for
controlling refrigerant flow therebetween;
FIG. 3 is a diagrammatic view of yet another embodiment of a heat
pump and air conditioning system in accordance with the present
invention showing a thermal storage device in serial connection
with both a first and a second heat exchanger and a first and a
second expansion device, bypass conduits for bypassing both the
first and the second expansion device, and a control apparatus for
controlling refrigerant flow therebetween;
FIG. 4 is a diagrammatic view of yet another embodiment of a heat
pump and air conditioning system in accordance with the present
invention showing a thermal storage device connected to a four-way
valve operating in conjunction with a pair of three-way valves to
selectively bypass a first heat exchanger or a second heat
exchanger, and a control apparatus for controlling operation of at
least the valves to control flow of refrigerant;
FIG. 5 is a diagrammatic view of yet another embodiment of a heat
pump and air conditioning system showing a thermal storage device
connected to a four-way valve and a control apparatus for
controlling flow of refrigerant therethrough;
FIG. 6 is a diagrammatic view of the heat pump and air conditioning
system of FIG. 2 incorporating a water heater;
FIG. 7 is an exploded view of one embodiment of a thermal storage
device in accordance with the present invention;
FIG. 8 is a partial sectional side view of the thermal storage
device of FIG. 7 showing phase change capsules positioned on a
series of grids;
FIG. 9 is a partial sectional top view of another embodiment of a
thermal storage device in accordance with the present invention
showing a cylindrical contained with phase change capsules disposed
among helical refrigerant coils;
FIG. 10 is a diagrammatic view of one embodiment of an air
conditioning or refrigeration system in accordance with the present
invention incorporating a thermal storage device, the system being
operable in a conventional cycle, a charging cycle, and a
discharging cycle;
FIG. 11 is a diagrammatic view of another embodiment of an air
conditioning or refrigeration system in accordance with the present
invention incorporating a thermal storage device and a refrigerant
pump, the system being operable in a conventional cycle, a charging
cycle, and a discharging cycle in which refrigerant can flow in
both a main flow loop and in a bypass line;
FIG. 12 is a diagrammatic view of yet another embodiment of a
heating and cooling system in accordance with the present invention
incorporating a thermal storage device and a refrigerant pump, the
system being operable in a conventional cycle, a charging cycle,
and a discharging cycle in which refrigerant can flow in both a
main flow loop and in at least one of two bypass lines;
FIG. 13 is a diagrammatic view of yet another embodiment of an air
conditioning or refrigeration system incorporating a thermal
storage device and a refrigerant pump, the system being operable in
a conventional cycle, charging cycles, and a discharging cycle in
which refrigerant can flow in both a main flow loop and in a bypass
line;
FIG. 14 is a diagrammatic view of yet another embodiment of a
heating and cooling system incorporating a thermal storage device
and a refrigerant pump, the system being operable in a conventional
cycle, a charging cycle, and a discharging cycle in which
refrigerant can flow in both a main flow loop and in a bypass line;
and
FIG. 15 is a diagrammatic view of still another embodiment of a
heating and cooling system incorporating a thermal storage device
and a refrigerant pump, the system being operable in a conventional
cycle, a charging cycle, and a discharging cycle in which
refrigerant can flow in both a main flow loop and in a bypass
line.
FIG. 16 is a diagrammatic view of an embodiment of a system
incorporating a thermal storage device which is operable in
conventional, charge, low temperature condensation discharge and
hot gas defrost cycles, wherein negative thermal potential is
collected during the hot gas defrost cycle and stored in the
thermal storage device.
FIG. 17 is a diagrammatic view of an embodiment of a refrigeration
system incorporating a thermal storage device for low-temperature
condensation of refrigerant.
FIG. 18 is a diagrammatic view of another embodiment of a
refrigeration system incorporating a thermal storage device for
low-temperature condensation of refrigerant, similar to that in
FIG. 17 except also being associated with a second refrigeration
system which charges the thermal storage device.
FIG. 19 is a diagrammatic view of an embodiment of a refrigeration
system incorporating a thermal storage device for low-temperature
condensation of refrigerant, similar to that in FIG. 18, wherein
negative thermal potential is collected during the hot gas defrost
cycle and stored in the thermal storage device.
FIG. 20 is a diagrammatic view of an embodiment of a refrigeration
system incorporating a thermal storage device for low-temperature
condensation of refrigerant, similar to that in FIG. 17, except
including only a single thermal exchange coil associated with the
thermal storage device.
FIG. 21 is a pressure-enthalpy (P-H) diagram of a refrigeration
cycle with low-temperature condensation in a thermal storage.
FIG. 22 is a P-H diagram of a refrigeration cycle with subcooling
and a cycle with a thermal storage.
FIG. 23 is a P-H diagram of a refrigeration cycle with a thermal
storage.
DETAILED DESCRIPTION OF THE DRAWINGS
The present invention relates to various flow schemes for thermal
storage-assisted heat pump and air conditioning systems and to
thermal storage devices particularly adapted for use in such
systems. The preferred flow schemes disclosed herein involve the
use of refrigerant-based systems. Halocarbon compounds including,
for example, freons such as R-22, are the preferred refrigerants
for use in systems of the present invention, although other
commercially available refrigerants such as ammonia can also be
used.
The illustrated preferred embodiments of flow schemes in accordance
with the present invention are heat pump systems which are designed
to function in both a heating mode and a cooling mode. In the
illustrated embodiments, refrigerant flow direction is changed (by
use of a four-way reversing valve) to effect the change between
heating mode and cooling mode. Those of ordinary skill in the art
will appreciate that refrigerant flow direction changeover is
simply one of several known means for changing the mode of
operation of a typical heat pump system. Other reversal schemes not
relying upon reversing valves, such as those reversal schemes set
forth in ASHRAE Handbook 1984 Systems (Table 1, p. 10.2), hereby
incorporated by reference, may also be used in accordance with the
claimed invention without otherwise changing the flow schemes
disclosed herein.
Alternatively, systems in accordance with the present invention may
be designed as air conditioning systems only--for example, systems
operating only in the cooling mode. Such systems would omit any
refrigerant flow reversing valve but would otherwise operate in
accordance with the flow schemes as described herein for cooling
mode operation.
One preferred flow arrangement is illustrated in FIG. 1. As shown
in FIG. 1, a heat pump system 10 includes a compressor 12
discharging a compressed refrigerant stream to a conduit 14. A
four-way reversing valve 16 receives the compressed refrigerant
stream from conduit 14 and communicates the compressed refrigerant
stream to either a conduit 18 or a conduit 20 depending upon
whether the system is operating in heating or cooling mode as
described further below. Four-way reversing valve 16 is a
commercially available valve typically pilot-operated by a solenoid
valve or other control arrangement as illustrated. Refrigerant
which has passed through system 10 is returned to reversing valve
16 and is communicated back to compressor 12 by way of a conduit
22.
Conduit 18 communicates refrigerant between four-way reversing
valve 16 and a three-way valve 24. Three-way valve 24 controls flow
between conduits 18, 26 and 28. Conduit 26 communicates refrigerant
between three-way valve 24 and a first heat exchanger 30. First
heat exchanger 30 is, for example, a standard refrigerant-to-air
heat exchanger including a controlled fan 32, although a standard
refrigerant-to-water heat exchanger using a water coil with a
regulating valve may also be used.
A conduit 34 communicates refrigerant between first heat exchanger
30 and a three-way valve 36. Three-way valve 36 controls flow
between conduits 34,38, and 40. Conduit 38 communicates refrigerant
between three-way valve 36 and an expansion device 42. Expansion
device 42 may be any one of a number of commercially available
expansion devices, such as a set of opposing flow thermostatic
expansion valves, a capillary device, or other appropriate devices.
Typical thermostatic expansion valves appropriate for use in
systems of the present invention are described, for example, in
ASHRAE Handbook 1988 Equipment pp. 19.3-19.4.
A conduit 44 communicates the refrigerant stream between expansion
device 42 and another three-way valve 46. Three-way valve 46
controls flow between conduits 44, 48 and 50. Conduit 48 joins
conduit 40 at a three-way (t) junction 52 with another conduit
54.
Conduit 54 extends between junction 52 and a thermal storage device
56. Thermal storage device 56 is preferably of the structure shown
in FIGS. 7-9, described further below. Optionally, a supplemental
heater 58 (shown in dashed lines) is positioned in thermal storage
device 56. Another conduit 60 extends between thermal storage
device 56 and a junction 62. Junction 62 joins conduit 60, conduit
28 and a conduit 64.
Returning to conduit 50, that conduit extends between three-way
valve 46 and a second heat exchanger 66. Second heat exchanger 66
is, for example, a standard refrigerant-to-air heat exchanger
including a controlled fan 68, although a standard
refrigerant-to-water heat exchanger using a water coil with a
regulating valve may also be used.
Another conduit 70 extends between second heat exchanger 66 and a
three-way valve 72. Three-way valve 72 controls flow between
conduits 70, 20 and 64. Conduit 20 extends between three-way valve
72 and four-way reversing valve 16 to complete the refrigerant
circuit.
Thus, in the embodiment of the present invention illustrated in
FIG. 1, thermal storage device 56 is effectively connected in
parallel with both first heat exchanger 30 and second heat
exchanger 66. The flow path of refrigerant through this system is
dependent upon control of the positions of four-way reversing valve
16 and three-way valves 24, 36, 46 and 72. Control is achieved
through use of controller 74. Controller 74 is wired to a
thermocouple or other temperature sensing means disposed in thermal
storage device 56 as indicated by dashed line 76. An additional
temperature sensor may be used to sense the temperature of the
space to be conditioned as well as the outdoor ambient temperature.
Controller 74 may also be wired to an ice-level sensor. Based upon
the sensed temperatures and other parameters which may be wired
into the system logic or input by the user, the controller controls
the positions of valve 16 (as indicated by dashed line 78), valves
24, 36, 46 and 72 (as indicated respectively by dashed lines 80,
82, 84 and 86), and controls whether fans 32 and 68 (as indicated
by dashed lines 88 and 90) are operating. Controller 74 also
controls the supplemental heater 58 as indicated by dashed line 83.
Controller 74 may, for example, include a microelectronic
programmable thermostat of the type manufactured by White-Rogers or
Honeywell operating in conjunction with an electronic time control
and otherwise modified in a fashion within the capability of the
ordinary artisan to perform the functions described herein. The
time controller may be programmed to switch between heating and
cooling modes and between charging and discharging cycles of those
modes to take advantage of time-of-day energy use billing.
In FIG. 2, another embodiment of a heat pump and air conditioning
system in accordance with the present invention is illustrated.
System 110 includes many components also used in system 10, as
reflected by like reference numerals between the drawings. For
example, compressor 112, four-way reversing valve 116, first heat
exchanger 130 and its fan 132, second heat exchanger 166 and its
fan 168, thermal storage device 156 and optional supplemental
heater 158, and controller 174 are essentially unchanged from the
embodiment of FIG. 1.
However, unlike the system 10 of FIG. 1, system 110 includes a
thermal storage device connected in series with the condenser and
the evaporator. In addition, system 110 includes a first bypass
conduit bypassing both the first heat exchanger and an expansion
device and a second bypass conduit bypassing the second heat
exchanger and an expansion device.
In particular, a three-way (T) junction 124 connects conduit 118
with conduits 126 and 128. Conduit 126 extends between junction 124
and first heat exchanger 130. Conduit 128 extends between junction
124 and a valve 134. A conduit 136 extends between valve 134 and a
junction 138. Junction 138 connects conduit 136 in fluid
communication with conduits 140 and 142. As will be further
described below, when valve 134 is open to flow between conduit 128
and conduit 136, refrigerant can bypass first heat exchanger 130
and first expansion device 154 by flowing through conduit 136 into
conduit 142 to junction 160 and into conduit 162, from which it can
pass into thermal storage device 156. Thus, conduits 128, 136 and
142 collectively provide a first bypassing first heat exchanger 130
and first expansion device 154.
Similarly, refrigerant flowing in conduit 164 toward junction 170
can bypass second expansion device 176 and second heat exchanger
166. Conduits 180, 194 and 197 collectively provide a second bypass
conduit operable when valve 196 is positioned to allow flow between
conduits 194 and 197.
System 110 further includes a pair of conduits 148 and 140
extending between a junction 146 and junction 138 and including a
valve 152 therein. Similarly, system 110 includes a pair of
conduits 184 and 188 extending between a junction 182 and a
junction 190 and including a valve 186. Conduits 148 and 140 (along
with conduit 142) allow bypass of expansion device 154 without
bypass of first heat exchanger 130 when valve 134 is closed and
valve 152 is open. Conduits 184 and 188 (along with conduit 192)
allow bypass of expansion device 176 without bypass of second heat
exchanger 166 when valve 196 is closed and valve 186 is open.
Controller 174 operates to manipulate valves 116, 134, 152, 186 and
196 under appropriate conditions as indicated by dashed lines 185,
187, 189, 191 and 193. Controller 174 also operates supplemental
heater 158 as indicated by dashed line 183 and fans 132 and 168 as
indicated by dashed lines 177 and 179.
System 210 illustrated in FIG. 3 also provides first and second
bypass conduits. Conduit 231 and conduit 234 cooperate to provide a
first bypass conduit for bypassing expansion device 236 when valve
233 is open to allow flow. Likewise, conduits 250 and 254 cooperate
to provide a second bypass conduit for bypassing expansion device
260 when valve 252 is open to allow flow. Here again, controller
274 manipulates valves 216, 233 and 252 appropriately as indicated
by dashed lines 276, 278 and 280. In addition, controller 274
operates supplemental heater 258 as indicated by dashed line 283,
and fans 232 and 268 as indicated by dashed lines 282 and 284.
System 310 illustrated in FIG. 4 provides a pair of three-way
valves 324 and 360 and a four-way valve 336. Four-way valve is not
a reversing valve, but is preferably a valve similar to those used
in hydraulic or wastewater applications.
Four-way valve 336 operates in conjunction with three-way valves
324 and 360 to provide means for selectively bypassing either first
heat exchanger 330 or second heat exchanger 366. For example,
three-way valve 324 may be positioned so that the refrigerant
stream is prevented from entering conduit 326 and is allowed to
enter conduit 328. The refrigerant stream in conduit 328 flows
through junction 354 to conduit 350, then through junction 348 to
reach conduit 346. Four-way valve 336 is positioned to block flow
from conduit 338. Likewise, valve 360 is positioned to block flow
from conduit 352.
Thus, refrigerant flow in conduit 346 enters thermal storage device
356, passes through conduit 344 to expansion device 342, and enters
conduit 340. Four-way valve 336 is positioned to allow flow from
conduit 340 to pass through to conduit 343, from which the flow
passes to second heat exchanger 366, conduit 362, and through to
conduit 320 with appropriate positioning of three-way valve 360.
Similarly, second heat exchanger 366 can be bypassed under
appropriate conditions by manipulation of the valves 336 and 360 as
will be described further below. Controller 374 operates to control
valves 324, 336 and 360 (as indicated by dashed lines 380, 376 and
378 respectively) as well as four-way reversing valve 316 (as
indicated by dashed line 372) and fans 332 and 368 (as indicated by
dashed lines 384 and 382 respectively) based upon conditions sensed
in thermal storage device 356 (as indicated by dashed line 370).
Controller 374 also operates supplemental heater 358 as indicated
by dashed line 383.
In system 410 of FIG. 5, an arrangement similar to that of FIG. 4
is illustrated. However, in FIG. 5, four-way valve 426 effectively
controls the direction of flow in a subsidiary refrigerant circuit
including an expansion device 438 and a thermal storage device 456.
That is, a conduit 434 extends between four-way valve 426 and
expansion device 438. Expansion device 438 is connected to thermal
storage device 456 by way of a conduit 440. Another conduit 428
extends between thermal storage device 456 and four-way valve 426
to complete the subsidiary circuit (also referred to herein as the
thermal storage circuit). By use of if controller 474 to manipulate
the position of four-way valve 426, the direction of refrigerant
flow in the thermal storage circuit can be altered, again based
upon conditions sensed in thermal storage device 456 as indicated
by dashed line 470. In addition, controller 474 operates
supplemental heater 458 as indicated by dashed line 483.
System 510 illustrated in FIG. 6 is a variation of system 110
disclosed in FIG. 2. In system 510, a domestic water heater 519 is
disposed between a conduit 518 and a conduit 529 to receive high
temperature compressed refrigerant exiting from compressor 512.
Water heater 519 is typically a standard water heater as is found
in most residences. A water heater bypass conduit 527 and a series
of valves 521 and 523 will also typically be included in systems of
the present design. Valves 521 and 523 are controlled by controller
574 as indicated by dashed line 577. In other aspects, system 510
operates similarly to system 110 of FIG. 2.
Preferred embodiments of thermal storage devices usable in
connection with the present invention are illustrated in FIGS. 7-9.
As shown in FIG. 7, one preferred embodiment of a thermal storage
device 610 in accordance with the present invention includes a
rectilinear insulated tank or container 612 defining an interior
region 614.
A bank of refrigerant coils 616 is disposed in interior region 614
to provide means for conducting a refrigerant stream through
interior region 614. Coil bank 616 includes an inlet 618 for
admitting a refrigerant stream and an outlet 620 for discharging
the refrigerant stream. As those of ordinary skill in the art will
appreciate, the precise number of coils 622 in coil bank 616 may be
varied according to the specific application. In addition, although
coil bank 616 includes staggered rows of uniform, U-shaped coils
622, the arrangement and geometry of the coils likewise may be
varied to meet requirements for specific applications.
A first, unencapsulated phase change material 624 (shown in its
liquid state in FIG. 8) is disposed in interior region 614.
Unencapsulated phase change material 624 is, for example, water,
although other art recognized chase change materials may also be
used. Unencapsulated phase change material 624 fills the
interstices between coils and thus serves as a thermal conduction
bath for transferring heat from coil bank 616. It also, of course,
serves as a phase change material itself.
Thermal storage device 610 also optionally includes a plurality of
stackable grids 626 disposed in interior region 614 in
spaced-apart, parallel relationship. Grids 626 include legs 628 to
allow for stacking, but may alternatively be provided with other
stacking means, or, for example, may be removably received in slots
formed in the inner walls of container 612. It will be appreciated
that a wide variety of arrangements can be used to maintain grids
626 in spaced-apart relationship within interior region 614.
The number of grids 626 used in interior region 614 will depend
upon the application. As will be described further below, for
expected operation in a predominantly cold climate, a generally
higher number of grids 626 will be used, while for operation in a
predominantly warm climate, a generally lower number of grids 626
will be used. Of course, grids 626 can be omitted altogether.
Grids 626 are provided with a plurality of elongated openings 630
sized to slidably receive coils 622 of coil bank 616. Thus, grids
626 can be placed in interior region 614 or removed therefrom
without disturbing coil bank 616.
An encapsulated phase change material 632 is also located in
interior region 614 and is immersed in unencapsulated phase change
material 624. For example, a plurality of phase change capsules 634
may be disposed upon grids 626 amidst coil bank 616. Capsules 634
may be filled 80-90% full with phase change material in its solid
state as shown in FIG. 8 to allow expansion space for encapsulated
material 632 during phase change, or may be filled nearly 100% full
with phase change material 632 in its liquid state. Typical phase
change materials for use in capsules 634 include formulations
comprising CaCl.sub.2. 6H.sub.2 O.
Phase change material 632 has a melt temperature that is higher
than that of phase change material 624. For example, a typical
system might use CaCl.sub.2. 6H.sub.2 O as the encapsulated phase
change material 632 (melt temperature about 27.degree. C.) and
H.sub.2 O as the unencapsulated phase change material (melt
temperature about 0.degree. C.).
A wide variety of art recognized geometry's for capsules 634 may be
used in the present invention. For example, capsules 634 may be
spherical, oblong, or may be for complex, irregular geometries to
allow nested stacking while maintaining space for immersion by
unencapsulated phase change material 624. In addition, capsules 634
may be formed of flexible material and filled to capacity with
phase change material 632 such that upon expansion or compression
of phase change material 632, the walls of capsules 634 are free to
flex.
Another embodiment of a thermal storage device in accordance with
the present invention is illustrated in FIG. 9. Thermal storage
device 710 includes an insulated cylindrical contained 712 defining
an interior region 714. A refrigerant coil 716 is disposed in
interior region 714, the refrigerant coil including an inlet 718
for admitting refrigerant and an outlet (not shown) for discharging
refrigerant.
Coil 716 is preferably a helical coil, although alternative
configurations are contemplated as within the scope of the present
invention. Coil 716 may, for example, comprise a plurality of
connected rings, each ring of equal diameter.
An unencapsulated phase change material 720, typically water, is
placed in interior region 714. In addition, another phase change
material 722 is encapsulated in capsules 724 and capsules 724 are
immersed in unencapsulated phase change material 720 in interior
region 714. Although grids may be provided to support layers of
capsules 724 in spaced-apart relationship, grids may be
omitted.
The internal thermal storage device configurations illustrated in
FIGS. 7-9 seek to maximize the surface are of phase change salt
presented for heat transfer by using encapsulation. In addition,
the inclusion of two types of phase change materials having
differing melt temperatures allows thermal storage and release over
a broader temperature range. The ability to easily vary the capsule
arrangement and number allows further advantage in adjusting the
temperatures and efficiencies for thermal storage and release.
The dimensions of container 612 (or container 712) can be varied
according to the desired application. It may be desirable, for
example, to provide a rectilinear container such as container 612
which is dimensioned to fit between wall or floor studs.
Alternatively, containers such as container 612 might themselves be
formed to serve as wall panels or floor panels. Containers may be
sized to fit conveniently in storage space available in a residence
(basement space, for example) or may even be buried outside the
building to be conditioned.
While containers 612 and 712 are typically closed, insulated steel
tanks as shown, alternative designs within the scope of the present
invention may rely upon different tank configurations. For example,
a relatively inexpensive open-top bulk storage container might be
used. In such designs, an insulating material is used which is
immiscible with the contained phase change material and less dense
than the phase change material when the material is in the liquid
state. For example, such insulating material might include
paraffins, mineral oil, or a mixture of such components. The
insulating material will be disposed in a stratified layer above
the contained phase change material to provide insulation. Such a
configuration may be particularly desirable where the contained
phase change material is a single, unencapsulated phase change
material, rather than the dual phase change material system
illustrated in the drawings.
I. Heating Mode
A. Charging Cycle
Under appropriate ambient conditions, the heat pump and air
conditioning systems of the present invention may be operating with
excess heating capacity--for example, during daytime winter
operation. This excess heating capacity is advantageously stored in
the form of latent heat in the thermal storage device by using the
thermal energy to liquefy the phase change material.
When system 10 of FIG. 1 is place in the charging cycle in heating
mode, four-way reversing valve 16 is positioned to allow flow of
compressed refrigerant from conduit 14 to conduit 18. The
refrigerant flows in conduit 18 toward three-way valve 24.
Controller 74 has operated to close three-way valve 24 to conduit
26 and to open three-way valve 24 to conduit 28. The gaseous
refrigerant stream thus flows into conduit 60 at junction 62.
Because controller 74 has closed flow form conduit 64 through valve
72, refrigerant is forced to enter conduit 60 at junction 62.
Gaseous refrigerant then passes from conduit 60 through thermal
storage device 56. The refrigerant transfers heat to the phase
change medium, melting it; the refrigerant, in turn, is liquefied.
Thermal storage device 56 therefore effectively acts as a
condenser. Predominantly liquid refrigerant is discharged into
conduit 54 and flows to junction 52. Controller 74 has positioned
three-way valve 46 to prevent flow from conduit 48 to conduit 50.
Thus, refrigerant passing through junction 52 flows into conduit
40. Controller 74 has positioned valve 36 to allow flow from
conduit 40 to conduit 38.
Predominantly liquid refrigerant flowing in conduit 38 passes
through expansion device 42 and exits into conduit 44. Controller
74 has positioned valve 46 to allow flow from conduit 44 through
valve 46 to conduit 50. Refrigerant then enters second heat
exchanger 66 (operating as an evaporator), where the refrigerant
evaporates and absorbs heat from the evaporator medium because
controller 74 has caused fan 68 to operate. Mainly gaseous, low
pressure refrigerant thus flows in conduit 70 through controlled
valve 72 to conduit 20 and then through four-way reversing valve 16
to reach conduit 22 to be returned to compressor 12. Controller 74
monitors the continuing charging cycle by sensing temperature in
thermal storage device 56 as indicated by dashed line 76 and also
by sensing the temperature of the space to be conditioned.
In system 110 of FIG. 2, controller 74 places the system in the
heating mode, charging cycle, by positioning valve 134 to allow
flow from conduit 128 to conduit 136. Valve 152 may be positioned
to block flow between conduits 148 and 140, although system
operation will be unaffected even if valve 152 remains in the open
position. In addition, valve 186 is positioned to block flow
between conduits 184 and 188 and valve 196 is positioned to block
flow between conduits 194 and 197. Thus, refrigerant flowing in
conduit 118 bypasses first heat exchanger 130 and first expansion
device 154, flowing to conduit 128 when it reaches junction 124 and
passing through valve 134 to conduit 136, then to conduit 142 to
conduit 162, thereafter entering thermal storage device 156. There,
the refrigerant transfers heat through the unencapsulated phase
change material to the encapsulated phase change material and then
exits through conduit 164.
Mainly liquid refrigerant then passes through junction 170 to
conduit 172 and through second expansion device 176, discharging to
conduit 178. Liquid refrigerant passes through junction 190 to
conduit 192 and passes through second heat exchanger 166, where the
refrigerant evaporates, absorbing heat from the evaporator medium.
Finally, the mainly gaseous refrigerant returns to compressor 112
by way of conduit 199, conduit 120, four-way reversing valve 116,
and conduit 122.
In system 210 of FIG. 3, controller 74 opens valve 233 to allow
refrigerant flow to bypass first expansion device 236. Further,
controller 74 closes valve 252 to force refrigerant to pass through
second expansion device 260. Thus, gaseous, high temperature
refrigerant flowing in conduit 218 passes through first heat
exchanger 230 with minimal heat loss (controlled fan 232 is not
operating at this time) and passes through conduit 224 to conduit
231. The refrigerant passes through valve 233 to conduit 234,
flowing to conduit 242 when it reaches junction 240.
Refrigerant enters thermal storage device 256 and exits in mainly
liquid form into conduit 244. The mainly liquid refrigerant then
passes through junction 246 to conduit 248 to reach second
expansion device 260, exiting into conduit 262. From there,
refrigerant passes to conduit 270, through second heat exchanger
266 (where fan 368 is operating), and returns to compressor via
conduits 220 and 222.
In system 310 of FIG. 4, controller 374 places the system in
heating mode, charging cycle, by positioning valve 324 to allow
flow from conduit 318 to conduit 328 while blocking flow through
conduit 326, thus bypassing first heat exchanger 330. Controller
374 also places four-way valve 336 in a position allowing flow only
from conduit 340 to conduit 343 to second heat exchanger 366.
Finally, controller 374 operates to set valve 360 to a position
allowing flow from conduit 362 to conduit 320 while blocking flow
from conduit 352.
Thus, refrigerant flowing in conduit 318 passes through valve 324
to conduit 328, through junction 354 to conduit 350, and through
junction 348 to conduit 346, where it enters thermal storage device
356. Mainly liquid refrigerant is discharged to conduit 344 and
passes through expansion device 342 to conduit 340, where it flows
through four-way valve 336 to reach conduit 343. From conduit 343,
the mainly liquid refrigerant flows through second heat exchanger
366 with fan 368 in operation. Finally, mainly gaseous refrigerant
returns to compressor 312 via conduits 362, 320 and 322.
In system 410 of FIG. 5, controller 474 manipulates valve 426 to
place the system in the heating mode, charging cycle. Specifically,
controller 474 positions valve 426 to allow flow from conduit 424
to conduit 428, and to allow flow from conduit 434 to conduit 436.
Thus, refrigerant in conduit 418 passes through first heat
exchanger 430 with minimal heat losses (fan 432 is off) and flows
through conduit 424, through valve 426, to conduit 428, reaching
thermal storage device 456. Mainly liquid refrigerant exits thermal
storage device 456, flowing through conduit 440 to reach expansion
device 438, then flows from conduit 434 through valve 426 to
conduit 436. Liquid refrigerant then passes through second heat
exchanger 466 and evaporates, thereafter returning to compressor
412 by way of conduits 420 and 422.
System 510 of FIG. 6 operates similarly to system 110 of FIG. 2 in
the heating mode, charging cycle. It is possible that valve 521 may
be closed and valve 523 opened in this configuration allowing flow
to bypass water heater 519 by way of bypass conduit 527.
B. Discharging Cycle
The heat pump and air conditioning systems of the present invention
operate in a discharging cycle in heating mode when the thermal
energy stored in the thermal energy storage device is called upon
for release to the system. That is, in the heating mode,
discharging cycle, at least part of the phase change medium in the
thermal storage device is in its liquid state. In the case where
unencapsulated and encapsulated phase change materials are both
used, both the unencapsulated phase change material and the
encapsulated phase change material are usually partially in their
liquid states. Thermal energy is discharged to the system by
causing at least part of the encapsulated phase change material to
return to its solid state, and is discharged as sensible heat from
both the encapsulated and unencapsulated phase change
materials.
In system 10 of FIG. 1 in heating mode, discharging cycle, four-way
reversing valve 16 is positioned to allow flow from conduit 14 to
conduit 18. Valve 24 is positioned to allow flow from conduit 18 to
conduit 26 while blocking flow to conduit 28, and valve 36 is
positioned to allow flow from conduit 34 to conduit 38 while
blocking flow to conduit 40. Valve 46 is set to allow flow from
conduit 44 to conduit 48 while blocking flow to conduit 50, and
valve 72 is set to allow flow from conduit 64 to conduit 20 while
blocking flow to conduit 70. As a result, in this configuration,
refrigerant bypasses second heat exchanger 66.
Accordingly, refrigerant in conduit 18 passes through valve 24,
through conduit 26, and into first heat exchanger 30 (with fan 32
on such that the first heat exchanger operates as a condenser),
where it is liquefied. The mainly liquid refrigerant flows through
conduit 34, conduit 38, expansion device 42, and conduit 44,
reaching valve 46. There, the refrigerant passes to conduit 48,
through junction 52, and into conduit 54 to enter thermal storage
device 56. In thermal storage device 56 (which operates as an
evaporator in this configuration), the liquid refrigerant stream
absorbs heat from the phase change material.
Mainly gaseous refrigerant exits thermal storage device 56 via
conduit 60 and passes through junction 62 to conduit 64. From
there, the refrigerant stream returns to compressor 12 by way of
conduits 20 and 22.
In system 110 of FIG. 2 in heating mode, discharging cycle,
controller 174 positions valve 134 to block flow between conduits
128 and 136, and positions valve 152 to block flow between conduits
148 and 140. Controller 174 may also position valve 186 to block
flow from conduit 184 to conduit 188 (although this is not
necessary to system operation in this configuration) and positions
valve 196 to allow flow from conduit 194 to conduit 197. Four-way
reversing valve 116 remains positioned to allow flow from conduit
114 to conduit 118. Fan 168 is off.
Thus, refrigerant in conduit 118 flows through junction 124 to
conduit 126 and through first heat exchanger 130 (with fan 132 on).
Refrigerant then passes through conduits 144 and 150, expansion
device 146, conduits 158 and 162, and thermal storage device 156.
Having absorbed heat in device 156, the mainly gaseous refrigerant
passes through conduits 164, 180, 194 and 197, returning to
compressor 112 via conduits 120 and 122.
In system 210 of FIG. 3 in heating mode, discharging cycle,
controller 274 has positioned valve 233 in its closed position
forcing refrigerant to flow through expansion device 236 and has
positioned valve 252 in its open position allowing refrigerant to
bypass expansion device 260. Four-way reversing valve is set to
direct flow from conduit 214 to conduit 218.
Thus, in discharging stored heat, compressed refrigerant in conduit
218 flows through first heat exchanger 230 (with fan 232 on) in
which it is condensed. The mainly liquid refrigerant then flows
through conduits 224 and 228 to reach expansion device 236. The
refrigerant then passes through conduits 238 and 242 to reach
thermal storage device 256, in which it absorbs heat from the phase
material contained therein and solidifies the phase change
material.
The mainly gaseous refrigerant then passes through conduit 244,
conduit 250, valve 252, conduit 254, and conduit 270 to reach
second heat exchanger 266 where fan 268 is off, such that heat
transfer is minimal. Finally, refrigerant returns to compressor 212
by way of conduits 220 and 222.
In system 310 of FIG. 4 in heating mode, discharging cycle,
controller 374 sets valve 324 to allow flow between conduits 318
and 326 while blocking flow from conduit 328. Controller 374 sets
valve 336 to allow flow from conduit 334 to conduit 340 and to
otherwise block flow. Valve 360 is positioned to allow flow from
conduit 352 to conduit 320.
Thus, refrigerant in conduit 318 passes through conduit 326 and
through first heat exchanger 330 (with fan 332 on) to reach conduit
334. The mainly liquid refrigerant passes through valve 336 to
conduit 340, through expansion device 342, conduit 344, and enters
thermal storage device 356. The refrigerant absorbs heat in device
356 and evaporates as noted with respect to previous embodiments.
The mainly gaseous effluent refrigerant passes through conduit 346
and conduit 352, returning to compressor 312 by way of conduits 320
and 322.
In system 410 of FIG. 5 in heating mode, discharging cycle,
controller 474 positions valve 426 to allow flow from conduit 424
to conduit 434 and to allow flow form conduit 428 to conduit 436.
In addition, controller 474 turns fan 432 on and fan 468 off. Thus,
refrigerant in conduit 418 passes through first heat exchanger 430
(with fan 432 on), conduit 424, conduit 434, expansion device 438,
conduit 440, and thermal storage device 456. After absorbing heat,
the mainly gaseous refrigerant flows through conduits 428 and 436,
through second heat exchanger 466 (with fan 468 off), and finally
through conduits 420 and 422 to reach compressor 412.
The system of FIG. 6 works in similar fashion to that of FIG.
2.
The mainly gaseous refrigerant exits through conduit 60 and passes
through junction 62 to conduit 28. It next passes through valve 24
to reach conduit 18, from which it returns to compressor 12 by way
of conduit 22.
In system 110 of FIG. 2 in cooling mode, charging cycle, valve 116
is positioned to allow flow from conduit 114 to conduit 120 rather
than to conduit 118. In addition, valve 196 is positioned to
prevent flow from conduit 197 to conduit 194, and valve 186 is
positioned to prevent flow from conduit 188 to conduit 184. Also,
valve 152 may be positioned to prevent flow from conduit 140 to
conduit 148 (although this is not necessary) and valve 134 is
positioned to allow flow from conduit 136 to conduit 128. Thus, in
this configuration, refrigerant flows through second heat exchanger
166, expansion device 176, and thermal storage device 156, but
bypasses expansion device 154 and first heat exchanger 130.
Specifically, refrigerant in conduit 120 passes through junction
198 to conduit 199 and reaches second heat exchanger 166 (with fan
168 on), where the refrigerant is liquefied. Refrigerant then
passes through conduit 192, through junction 190 to conduit 178,
and through expansion device 176. Refrigerant next flows through
conduit 172, junction 170, and conduit 164 to enter thermal storage
device 156, where it absorbs heat and evaporates while solidifying
the phase change material in thermal storage device 156.
Mainly gaseous refrigerant exiting thermal storage device 156
passes through conduit 162, through junction 160 to conduit 142,
and through junction 138 to conduit 136. From there the refrigerant
passes through valve 134 to conduit 128, thus bypassing first heat
exchanger 130 (with fan 132 off). Finally, the refrigerant returns
to compressor 112 by way of conduits 118 and 122.
In system 210 of FIG. 3 in cooling mode, charging cycle, four-way
reversing valve is set to allow flow from conduit 214 to conduit
220, valve 252 is closed to force refrigerant to flow through
expansion device 260, and valve 233 is open to allow refrigerant to
bypass expansion device 236. Thus, refrigerant flows in conduit 220
through second heat exchanger 266 (now acting as a condenser with
fan 268 operating) and passes through conduit 270, junction 264,
and conduit 262 to reach expansion device 260. the mainly liquid
refrigerant then flows through conduits 248 and 244 to reach
thermal storage device 256. The mainly liquid refrigerant absorbs
heat in the thermal storage device and evaporates, and at least the
encapsulated phase change material solidifies. The mainly gaseous
refrigerant then flows through conduit 242, junction 240, conduit
234, and through valve 233 to conduit 231. From there it passes
through junction 226 to conduit 224 and flows through first heat
exchanger 230 (with fan 232 off such that heat losses are minimal).
The mainly gaseous refrigerant then returns to compressor 212 by
way of conduits 218 and 222.
In system 310 of FIG. 4 in cooling mode, charging cycle, three-way
valve 360 is positioned to allow flow from conduit 320 to conduit
362 while blocking flow to conduit 352. Four-way valve 336 is
positioned to allow flow from conduit 343 to conduit 340. Three-way
valve 324 is positioned to allow flow form conduit 328 to conduit
318 while blocking flow from conduit 326, thus forcing refrigerant
to bypass first heat exchanger 330. Thus, refrigerant in conduit
320 passes through conduit 362, second heat exchanger 366 (with fan
368 operating), conduit 343, conduit 340, expansion device 342,
conduit 344 and thermal storage device 356, in which it evaporates.
Mainly gaseous refrigerant passes through conduits 346, 350 and
328, finally returning to compressor by way of conduits 318 and
322.
In system 410 of FIG. 5 in cooling mode, charging cycle, for-way
valve 426 is positioned to allow flow from conduit 436 to conduit
434 and from conduit 428 to conduit 424. Thus, refrigerant in
conduit 420 passes through second heat exchanger 466 (with fan 468
on), conduit 436, conduit 434, expansion device 438, conduit 440
and thermal storage device 456. After absorbing the thermal energy,
mainly gaseous refrigerant passes through conduit 428, conduit 424
and first heat exchanger 430 (with fan 432 off), returning then to
compressor 412 by way of conduits 418 and 422.
System 510 of FIG. 6 works similarly to system 210 of FIG. 2.
B. Discharging Cycle
During system operation during times of high cooling demand--for
example, daytime summer operation--the heat pump and air
conditioning system of the present invention is configured to
discharge stored "coolness" from the phase change material in the
thermal energy storage device, thereby reducing overall system
power consumption and increasing system cooling capacity. System
operation in the cooling mode, discharging cycle is in many
respects analogous to operation in the heating mode, charging
cycle.
In system 10 of FIG. 1 in cooling mode, discharging cycle, four-way
reversing valve 16 is set to allow flow from conduit 14 to conduit
20 and from conduit 18 to conduit 22. In addition, valve 72 is
positioned to allow flow from conduit 20 to conduit 64, blocking
flow to conduit 70. Valve 46 is positioned to block flow to conduit
50, while allowing flow from conduit 48 to conduit 44. Valve 36 is
positioned to allow flow from conduit 38 to conduit 34 while
blocking flow from conduit 40. Finally, valve 24 is positioned to
block flow from conduit 28 while allowing flow from conduit 26 to
conduit 18. Thus, refrigerant bypasses second heat exchanger 66
(fan 68 is off) but passes through first heat exchanger 30.
In particular, refrigerant in conduit 20 passes through conduit 64
and conduit 60 to reach thermal storage device 56, where the
refrigerant absorbs "coolness" from the solidified phase change
materials. The refrigerant liquefies and at least the
unencapsulated phase change material melts. The mainly liquid
refrigerant exits by way of conduit 54, then passes through conduit
48, conduit 44, expansion device 42, conduit 38, conduit 34 and
first heat exchanger 30 (with fan 32 on). Finally, the refrigerant
passes through conduits 26, 18 and 22 to return to compressor
12.
In system 110 of FIG. 2 in cooling mode, discharging cycle,
controller 174 positions valve 196 to allow flow from conduit 197
to conduit 194 and may position valve 186 to block flow between
conduits 184 and 188, although this is not necessary. In addition,
controller 174 positions valve 152 to prevent flow between conduits
140 and 148 and positions valve 134 to prevent flow between
conduits 136 and 128. Thus, refrigerant in conduit 120 flows
through conduits 197, 194, 180 and 164 to reach thermal storage
device 156, where it absorbs "coolness" and liquefies. The mainly
liquid refrigerant then flows through conduits 162 and 158, passes
through first expansion device 154, and flows through conduits 150
and 144 to reach first heat exchanger 130 (with fan 132 on). From
there, the refrigerant stream returns to compressor 112 by way of
conduits 126, 118 and 122.
In system 210 of FIG. 3 in cooling mode, discharging cycle,
controller 274 positions valve 252 to allow flow from conduit 254
to conduit 250 and positions valve 233 to block flow from conduit
234 to conduit 231. Thus, refrigerant in conduit 220 flows through
second heat exchanger 266 (with fan 268 off such that heat losses
are minimal), conduits 270 and 254, conduit 250, and conduit 244 to
enter thermal storage device 256. There, it absorbs "coolness" and
liquefies, exiting through conduit 242 and passing from there
through conduit 238, first expansion device 236, and conduits 228
and 224 to reach first heat exchanger 230 (with fan 232 on).
Finally, the refrigerant stream returns to compressor 212 by way of
conduits 218 and 222.
In system 310 of FIG. 4 in cooling mode, discharging cycle, valve
360 is positioned to allow flow from conduit 320 to conduit 352,
valve 336 is positioned to allow flow from conduit 340 to conduit
334, and valve 324 is positioned to allow flow from conduit 326 to
conduit 318. Thus, refrigerant in conduit 320 flows through conduit
352 and conduit 346 to reach thermal storage device 356.
Refrigerant exits thermal storage device 356 and flows through
expansion device 342, conduit 340, conduit 334, and first heat
exchanger 330 (with fan 332 on).Refrigerant exits to conduit 326
and passes from thereto compressor 312 by way of conduits 318 and
322.
In system 410 of FIG. 5, valve 426 is positioned to allow flow from
conduit 436 to conduit 428 and to allow flow from conduit 434 to
conduit 424. In addition, controller 474 operates to turn fan 468
off and fan 432 on. Thus, refrigerant in conduit 420 flows through
second heat exchanger 466 (with fan 468 off), conduit 436 and
conduit 428 to reach thermal storage device 456, where it transfers
heat with the phase change material contained therein. The mainly
liquid effluent refrigerant stream flows through conduit 440,
expansion device 438, and conduit 434, then passes through four-way
valve 426 to conduit 424 to reach first heat exchanger 430 (with
fan 432 on). The refrigerant stream exits into conduit 418 and
returns to compressor 412 via conduit 422.
System 510 of FIG. 6 operates in similar fashion to system 110 of
FIG. 2.
III. Bypass Mode
For operation of the systems of the present invention in certain
conditions, it may not be necessary to store or retrieve thermal
energy from the thermal energy storage device. Thus, the systems of
the present invention provide for effective bypass of the thermal
storage device under appropriate conditions.
In system 10 of FIG. 1 operating in bypass mode, controller 74
positions valve 24 to allow refrigerant flow between conduits 18
and 26, and positions valve 36 to allow flow between conduits 34
and 38. Further, controller 74 positions valve 46 to allow flow
between conduits 44 and 50, and positions valve 72 to allow flow
between conduits 70 and 20. Thus, refrigerant passes through first
heat exchanger 30 (with fan 32 on), expansion device 42, and second
heat exchanger 66 (with fan 68 on) but bypasses thermal storage
device 56. Controller 74 may set four-way reversing valve 16 to
allow flow from conduit 14 to conduit 18, or alternatively may set
valve 16 to allow flow from conduit 14 to conduit 20.
In system 110 of FIG. 2, controller 174 closes valve 134, blocking
flow between conduits 128 and 136, and likewise closes valve 1961,
blocking flow between conduits 194 and 197. Valves 152 and 186 may
be closed or open, depending upon flow direction. That is, where
flow from compressor 112 and conduit 114 is directed to conduit
118, valve 152 is open and valve 186 is closed. Thus, in this
configuration, refrigerant passes through first heat exchanger 130
(with fan 132 on), bypasses first expansion device 154, then passes
through thermal storage device 156, second expansion device 176,
and second heat exchanger 166 (with fan 168 on). However, although
refrigerant passes through thermal storage device 156, the
temperature of the refrigerant stream is such that no phase change
occurs. The thermal storage device 156 is therefore effectively
"bypassed" in this configuration.
Alternatively, where flow from compressor 112 and conduit 114 is
directed to conduit 120, valve 152 is closed and valve 186 is open.
That is, in this configuration, refrigerant flows through second
heat exchanger 166 (with fan 168 on), thermal storage device 156,
first expansion device 154, and first heat exchanger 130 (with fan
132 on). Here again, the no phase change occurs in thermal storage
device 156; the device is effectively "bypassed".
In system 210 of FIG. 3 in bypass mode, controller 274 positions
valves 233, 252 in either open or closed positions, depending flow
direction. Where flow from compressor 212 and conduit 214 is
directed to conduit 218, valve 233 is open and valve 252 is closed,
such that refrigerant flows through first heat exchanger 230 (with
fan 232 on), thermal storage device 256 (no phase change
occurring), second expansion device 260, and second heat exchanger
266 (with fan 268 on). Alternatively, where flow from compressor
212 and conduit 214 is directed to conduit 220, refrigerant flows
through second heat exchanger 230 (with fan 232 on), thermal
storage device 256 (with fan 268 on), first expansion device 236,
and first heat exchanger 230 (with fan 232 on).
In system 310 of FIG. 4, where flow from compressor 312 and conduit
314 is directed to conduit 318, controller 374 positions valve 324
to allow flow between conduits 318 and 326 and positions valve 360
to allow flow between conduits 362 and 320. Further, controller 374
positions four-way valve 336 to allow flow between conduits 334 and
338 and between conduits 340 and 343. Thus, refrigerant passes
through first heat exchanger 330 (with fan 332 on), thermal storage
device 356 (no phase change occurring), expansion device 342, and
second heat exchanger 366. Alternatively, where flow is reversed,
controller 374 manipulates valves 360, 336 and 324 so that
refrigerant flows through second heat exchanger 366 (with fan 368
on), thermal storage device 356 (no phase change occurring),
expansion device 342, and first heat exchanger 330 (with fan 332
on).
In system 410 of FIG. 5, where flow is from compressor 412 through
conduit 414 to conduit 418, controller 474 positions four-way valve
426 to allow flow between conduits 424 and 428 and between conduits
434 and 436. Thus, refrigerant passes through first heat exchanger
430 (with fan 432 on), thermal storage device 456 (no phase change
occurring), expansion device 438 and second heat exchanger 466
(with fan 468 on). Again, where flow is reversed, controller 474
manipulates valve 426 to allow flow from conduit 436 to conduit 428
and from conduit 434 to conduit 424. Thus, in this configuration,
refrigerant flows through second heat exchanger 466 (with fan 468
on), thermal storage device 456 (no phase change occurring),
expansion device 438, and first heat exchanger 430 (with fan 432
on).
System 510 of FIG. 6 operates similarly to system 110 of FIG. 2 in
bypass mode.
IV. Mixed Mode
Systems in accordance with the present invention may also be
operated in a "mixed" mode in which refrigerant flows in parallel
through both a heat exchanger and the thermal storage device. For
example, in system 10 of FIG. 1, controller 74 may position valve
24 to allow a portion of refrigerant flow in conduit 18 to enter
conduit 26, while allowing another portion to enter conduit 28.
Valve 36 in turn is positioned to receive flow from both conduits
36 and 40, delivering the combined flow to conduit 38. Fans 32 and
68 both typically operate in this configuration, although fan 36
may be controlled to operate at a lower speed.
The system may be operated in mixed mode to achieve either heating
or cooling, and either thermal storage charging or discharging. For
example, the system may operate in mixed mode to serve a light
heating demand in one portion of a space to be conditioned while
simultaneously operating to charge the thermal storage device.
In another mixed mode configuration particularly applicable to the
systems of FIGS. 3 and 5, the fans of the first and second heat
exchangers can be run at lower speed so that liquefying of the
refrigerant is carried out in part in the thermal storage device,
and partly in one of the heat exchangers. Analogously, partial
evaporation can be carried out in the thermal storage device and in
one of the heat exchangers.
V. Additional Embodiments
Another embodiment on an air conditioning or refrigeration system
in accordance with the present invention is illustrated in FIG. 10.
In this embodiment, system 1010 includes a main flow loop including
a compressor 1012, an outside coil 1014, an inside coil 1016, and a
thermal storage device 1018. As shown, thermal storage device 1018
is positioned in a first bypass line extending from the outlet of
outside coil 1014 to the outlet of inside coil 1016, thus allowing
inside coil 1016 to be completely bypassed as described below.
In the "conventional" cycle as that term is used in connection with
the embodiments of FIGS. 10-14, the thermal storage device is
bypassed completely. For operation of system 1010 in a conventional
cycle, valves 1026 and 1028 are open, while valves 1024 and 1030
are closed. Thus, refrigerant from compressor 1012 flows through
outside coil 1014 and then through metering device 1020 and open
valves 1026 and 1028 ultimately reaching inside coil 1016. From
inside coil 1016, refrigerant flows back to compressor 1012.
Typically, system 1010 might be operated in its conventional cycle
during off-peak hours in which there is no need to take advantage
of energy which may be stored in the phase change materials
contained in thermal storage device 1018. Thus, stored energy in
device 1018 can be maintained for use during on-peak operation
periods.
Air conditioning or refrigeration system 1010 can also be operated
to store cooling capacity during off-peak hours for on-peak
recovery. For example, where the phase change material contained in
thermal storage device 1018 is water, the water can be frozen and
cooling capacity thus can be stored. In this cycle, referred to
herein as a "charging cycle", valves 1024 and 1026 are closed,
while valves 1028 and 1030 are open. Accordingly, refrigerant flows
from compressor 1012 through outside coil 1014, metering device
1020 and thermal storage device 1018. Because valve 1028 is open,
refrigerant bypasses metering device 1022. Because valve 1030 is
open, refrigerant can flow through the second bypass line bypassing
completely inside coil 1016 and returning directly to compressor
1012.
System 1010 can also be operated in a discharging cycle to
discharge stored energy during peak demand periods. Here, valve
1024 is open (allowing metering valve 1020 to be bypassed), while
valves 1026, 1028 and 1030 are closed. In this configuration,
refrigerant or working fluid flows from compressor 1012, through
outside coil 1014, through open valve 1024, and from there directly
to thermal storage device 1018. Upon leaving thermal storage device
1018, refrigerant flows through metering device 1022 and then
through inside coil 1016 before returning to compressor 1012.
Advantageously, system 1010 may allow the elimination of one or
more stages of the compressor. That is, a single-stage compressor
in this configuration works as a first stage of a two-stage
compressor in the discharging cycle and as a second stage of a
two-stage compressor in the charging cycle. Advantageously, then,
multi-stage compressors may in some circumstances be replaced with
single-stage compressors in systems in configured in accordance
with the present invention.
For example, if system 1010 were operated solely in the
conventional cycle (i.e. with no use of thermal storage) using R-22
refrigerant (condensing temperature 130.degree. F. (54.degree. C.),
evaporating temperatures -40.degree. F. (-40.degree. C.)) and a
single-stage compressor, the compressor ratio would be unacceptably
high, approximately 20.5 (the discharge pressure at the compressor,
311.5 psia (21.5 MPa), divided by the suction pressure, 15.2 psia
(0.104 MPa)). Yet using a multi-stage compressor in the system
would create complications.
On the contrary, by providing system 1010 with the capability to
utilize thermal storage device 1018 in both the charging and
discharging cycles, a single-stage compressor can be used and the
compressor ratios will be well within acceptable limits. In the
charging cycle, assuming that water is used as the phase change
material, the refrigerant temperature would need to be reduced from
130.degree. F. (54.degree. C.) to about 22.degree. F. (-5.degree.
C.) to freeze the phase change materials at 32.degree. F.
(0.degree. C.). The compressor acts as the second stage of a
two-stage compressor, and the compressor ratio is only about 5.2.
Similarly, in the discharging cycle, in which the compressor acts
as the first stage of a two-stage compressor, the compressor ratio
would be about 5.71, again within acceptable limits.
As an additional feature of the present invention, thermal storage
device 1018 may be designed to work not only as a condenser, but
also as a downstream "subcooler" in the discharging cycle. This may
be accomplished by providing a pair of heat exchanger coils 1032
and 1034 extending through the interior of thermal storage device
1418. A valve 1036 is also provided to interrupt flow through one
of the coils (coil 1034 in FIG. 10). In this configuration,
refrigerant is condensed in outside coil 1014, then flows through
valve 1024. The refrigerant (now primarily liquid) is subcooled in
coil 1032 in thermal storage device 1018 while being blocked by
closed valve 1036 from flowing through coil 1034. That is, because
refrigerant flow through coil 1034 is blocked, heat transfer
between the phase change materials and the refrigerant occurs only
through coil 1032. Consequently, thermal storage device 1018 does
not work as a condenser in this configuration.
Refrigerant exiting from thermal storage device 1018 in coil 1032
passes through metering device 1022 and then passes through inside
coil 1016, returning to compressor 1012 as described above. Those
of ordinary skill in the art will appreciate that a dual-coil
arrangement such as has been described and illustrated with regards
to this embodiment may also be incorporated into the other
embodiments of the present invention described below.
Tests of system 1010 have shown that it is capable of achieving
better evaporation temperatures than standard systems having no
thermal storage capability. For example, when a reciprocating
compressor (EADB-0200-CAB, manufactured by Copeland) was used in
system 1010, an evaporating temperature of -62.degree. F.
(-52.degree. C.) was achieved, as compared to 040.degree. F.
(-40.degree. C.) for a standard system. When a scroll compressor
(23ZR, manufactured by Copeland) was used in system 1010, an
evaporating temperature of -40.degree. F. (-40.degree. C.) was
achieved, as compared to -20.degree. F. (-29.degree. C.) in a
standard system.
Yet another embodiment of the present invention is illustrated in
FIG. 11. As shown, a system 1110 includes a main flow loop
including a compressor 1112, outside and inside coils 1114 and
1116, and a thermal storage device 1118. Thermal storage device
1118 is positioned in a bypass line extending between the outlet of
outside coil 1114 and the outlet of inside coil 1116, allowing
inside coil 1116 to be bypassed.
Also included are metering devices 1120 and 1122, valves 1124 and
1126, and optional valve 1128. Metering device 1120 is located in
the bypass line, while metering device 1122 is located in the main
flow loop. Valves 1124 and 1128 are located in the bypass line, and
valve 1126 is located in the main flow loop. A controller 1140 may
also be provided.
System 1110 also includes a working fluid pump 1130 positioned
between thermal storage device 1118 and the inlet of inside heat
exchanger 1116. Pump 1130 may be any of a variety of standard
refrigerant pumps well known to those of ordinary skill in the art,
including, for example, metering pumps and centrifugal pumps.
For operation of the embodiment of FIG. 11 in the conventional
cycle, valves 1124 and 1128 are closed to flow, while valve 1126 is
open. Refrigerant exiting compressor passes through outside coil
1114, valve 1126, metering device 1122, and inside coil 1116, thus
bypassing thermal storage device 1118. It then returns to
compressor 1112.
Air conditioning/refrigeration system 1110 can also be operated in
a charging cycle in which valves 1124 and 1128 are opened, while
valve 1126 is closed. Refrigerant exiting compressor 1112 travels
through outside coil 1114 and through open valve 1124 and metering
device 1120 to reach thermal storage device 1118. After absorbing
heat from the phase change materials in thermal storage device
1118, refrigerant passes through open valve 1128 and returns to
compressor 1112. Thus, the phase change materials inside thermal
storage device 1118 freeze as a result of direct expansion of the
refrigerant or other working fluid. Advantageously, thermal storage
device 1118 effectively works as an evaporator in this
configuration.
System 1110 can then be operated to discharge stored cooling
capacity during peak demand periods. Refrigerant flow is initiated
in the bypass line by closing off valves 1124 and 1126, while
leaving valve 1128 open. Compressor 1112 is taken off-line in this
configuration. Pump 1130 is operated to cause mainly liquid
refrigerant to flow to inside coil 1116, where it picks up heat and
discharges "coolness" to the space to be conditioned. The
refrigerant, now primarily vapor, passes through open valve 1128 to
return to thermal storage device 1118. Advantageously, the power
requirements for pump 1130 are relatively low, allowing the use of
alternative energy sources including solar, battery, wind, and
co-generation for on-peak discharge.
Refrigerant flow can also simultaneously be initiated in the main
flow loop by opening valve 1126 and turning on compressor 1112.
Thus, hot refrigerant exiting compressor 1112 passes through
outside coil 1114, in which it is liquefied. Because valve 1124 is
closed, the liquid refrigerant exiting outside coil 1114 is forced
to flow through open valve 1126 and then through metering device
1122.
At junction 1134, the flow of refrigerant from metering device 1122
is joined by the refrigerant flow being pumped from pump 1130. The
combined flow then passes through inside coil 1116 for discharge to
the space being cooled. At junction 1136, the vapor flow can branch
off through open valve 1128 to return to thermal storage device
1118, and can also return to compressor 1112.
Advantageously, system 1110 can achieve very rapid cool-down by
using the simultaneous discharging cycles in both the main flow
loop and the bypass line as described above. That is, system 1110
stores cooling capacity in offpeak hours and uses that stored
cooling capacity to shave peak load during the on-peak hours. In
current refrigeration systems, designers typically provide excess
cooling capacity to adequately attempt to handle rapid cooling and
extremely high ambient temperatures during peak demand periods. No
such excess capacity is needed for systems of the present invention
because thermal storage device 1118 is not called upon to play the
role of a "coolness" accumulator to condense vapor after it exits
inside coil 1116.
In addition, the illustrated system 1110 may enable significant
reductions in compressor capacity as compared to similar systems
without loss in performance. A 2-ton compressor, for example, may
be usable where a conventional system would have required a 4-ton
compressor.
Another embodiment of the present invention is illustrated in FIG.
12. In this embodiment, the illustrated system may be operated as
both a heat pump and as an air conditioning or refrigeration
system. As shown, a heat pump and air conditioning/refrigeration
system 1210 includes a compressor 1212, outside and inside coils
1214 and 1216, and a thermal storage device 1218. Metering devices
1220, 1222, and 1224 are provided. In addition, a reversing valve
1226 as well as valves 1228, 1230, 1232, and 1234 are also
provided. System 1210 also includes a refrigerant pump 1240 as
described in connection with the embodiment illustrated in FIG. 11.
A controller 1252 may also optionally be provided. Likewise, a
liquid separator 1250 may be provided.
For operation in the conventional cycle as a heat pump/air
conditioning system, valve 1232 is opened while valves 1228, 1230,
and 1234 are all closed. This allows refrigerant to flow from
compressor 1212 through reversing valve 1226 to outside coil 1214,
and then through open valve 1232 and through metering device 1222
to inside coil 1216. From there, refrigerant can return to
compressor 1212 by way of reversing valve 1226. Thermal storage
device 1218 is completely bypassed in this cycle. Of course, by
changing the position of reversing valve 1226, refrigerant flow can
be reversed and the above-described steps carried out in reverse
order.
System 1210 can also be operated as a heat pump incorporating
thermal storage device 1218. For operation of system 1210 as a heat
pump in a charging cycle, valves 1230 and 1234 are opened, while
valves 1228 and 1232 are closed. Refrigerant flows from compressor
1212 through 1226, which is positioned to direct flow to conduit
1236.
Because valve 1234 is open, the refrigerant in conduit 1236 can
flow through valve 1234 to reach thermal storage device 1218,
releasing heat to the phase change materials contained within
device 1218. Refrigerant then exits thermal storage device 1218 and
flows through metering device 1220. Because valve 1230 is also
open, refrigerant can flow to outside coil 1214, thereafter
returning to compressor 1212 by way of reversing valve 1226. An
optional auxiliary heater 1242 may also be sued to assist in
charging the phase change materials in thermal storage device
1218.
With the present embodiment, the discharging cycle (for heat pump
operation) can occur either in one of two bypass flow loops or
simultaneously in both the main flow loop and in one of the bypass
flow loops. To initiate flow in a first of the bypass flow loops,
valve 1228 is open, but valves 1230, 1232, and 1234 are all closed.
Refrigerant exiting compressor 1212 and passing through reversing
valve 1226 is directed through conduit 1236, but cannot thereafter
pass through valve 1234 because that valve is closed. Thus,
refrigerant must flow through inside coil 1216.
Upon exiting inside coil 1216, refrigerant flows through metering
device 1224 to reach thermal storage device 1218. There it absorbs
energy from the phase change materials contained within device
1218. Because valve 1230 is closed and valve 1228 is open,
refrigerant flowing in conduit 1238 can pass through valve 1228 to
return to compressor 1212 by way of reversing valve 1226.
In a second of the bypass flow loops in the discharging cycle,
valve 1234 is opened and valve 1228 is closed. Valves 1230 and 1232
remain closed. In addition, pump 1240 is turned on, and compressor
1212 is turned off.
Thus, refrigerant passes through inside coil 1216, releasing heat
and liquefying, and then (flowing in a clockwise direction) passes
through junction 1246 and through pump 1240. Once it passes pump
1240, refrigerant can pass through thermal storage device 1218,
absorbing energy and evaporating.
Upon exiting thermal storage device 1218, refrigerant can pass
through open valve 1234 to recirculate through inside coil 1216.
Optionally, an auxiliary heater 1242 can be provided to operate in
connection with the phase change materials contained within thermal
storage device 1218 to provide additional energy to the incoming
refrigerant stream.
To operate system 1210 in the discharging cycle with simultaneous
flow in both the main flow loop and in one of the bypass flow
loops, valves 1232 and 1234 are both opened, while valves 1228 and
1230 are both closed. Pump 1240 and compressor 1212 are turned
on.
Accordingly, the primarily vapor refrigerant exiting compressor
1212 and passing through reversing valve 1226 is directed through
conduit 1236 to junction 1248. At the same time, refrigerant is
pumped by pump 1240 through thermal storage device 1218. The
primarily vapor refrigerant stream exiting thermal storage device
1218 flows through open valve 1234, also reaching junction 1248.
Thus, the two primarily vapor refrigerant streams join at junction
1248 and the combined flow passes through inside coil 1216,
releasing heat there and condensing.
The now primarily liquid refrigerant stream exits inside coil 1216
and flows to junction 1246. At junction 1246, a portion of the
refrigerant flows to pump 1240 and is subsequently pumped through
thermal storage device 1218 as previously described. The remainder
of the refrigerant flows through metering device 1222, open valve
1232, and outside coil 1214, returning to compressor 1212 by way of
reversing valve 1226.
System 1210 can also be operated as an air conditioner. For
operation in the charging cycle, valves 1230 and 1234 are open, and
valves 1228 and 1232 are closed. Reversing valve 1226 is positioned
to direct flow from compressor 1212 to conduit 1244.
Because valve 1228 is closed, refrigerant passes from conduit 1244
through outside coil 1214. Refrigerant then passes through open
valve 1230, through metering device 1220, and into thermal storage
device 1218, absorbing energy from the phase change materials
within device 1218. Upon exiting thermal storage device 1218,
refrigerant passes through open valve 1234 and can return to
compressor 1212 by way of reversing valve 1226.
Operation of the air conditioner in a discharging cycle proceeds
simultaneously in the main flow loop and in the bypass line as
described with regards to the system illustrated in FIG. 11. To
initiate flow in the bypass line, valve 1234 is opened; valves
1228, 1230, and 1232 are all closed; pump 1240 is turned on; and
compressor 1212 is turned off.
Consequently, liquid refrigerant is pumped by pump 1240 through
junction 1246 to inside coil 1216, and gaseous refrigerant passes
from there through open valve 1234 to reach thermal storage device
1218, where the gaseous refrigerant is liquefied. Upon exiting
thermal storage device 1218, refrigerant is forced to return to
pump 1240 because valves 1228 and 1230 are closed.
To initiate flow in the main flow loop in the discharging cycle,
valve 1232 is also opened. Valve 1234 remains open, and valves 1228
and 1230 remain closed. In addition, compressor 1212 is turned on.
Thus, refrigerant in conduit 1244 can flow through outside coil
1214, and through open valve 1232 and metering device 1222,
eventually reaching junction 1246. There, the refrigerant joins
refrigerant pumped by pump 1240 from thermal storage device 1218.
The combined flow passes through inside coil 1216, releasing
"coolness" to the space being conditioned. Upon exiting inside coil
1216, the flow can branch off, passing through open valve 1234 to
return to thermal storage device 1218. The flow also passes into
conduit 1236 and then returns to compressor 1212 by way of
reversing valve 1226.
Another embodiment of the present invention is illustrated in FIG.
13. As shown, an air conditioning or refrigeration system 1310
includes a compressor 1312, outside and inside coils 1314 and 1316
respectively, and a thermal storage device 1318. System 1310
further includes a single metering device 1320 and a pair of valves
1322 and 1324 respectively. A refrigerant pump 1326 is provided.
Optionally, a liquid refrigerant separator 1330 may be provided
upstream of compressor 1312. A controller 1340 can also be
provided.
System 1310 is operable as an air conditioner or a refrigeration
system in conventional, charging and discharging cycles. For
operation in the conventional cycle, valve 1322 is closed and valve
1324 is open. In addition, compressor 1312 is operating, and pump
1326 is not operating. As noted with regards to previous
embodiments, additional valving in line 1328 may be needed to block
unwanted flow through pump 1326 if, for example, pump 1326 is a
centrifugal pump.
Accordingly, in this configuration, refrigerant flows from
compressor 1312, through outside coil 1314, and then through
metering device 1320. Because valve 1322 is closed, refrigerant
bypasses thermal storage device 1318 entirely, flowing instead
through open valve 1324 to reach inside coil. Once the refrigerant
flows through inside coil 1316, it returns to compressor 1312,
passing through liquid separator 1330 if such is provided.
For operation of system 1310 in the charging cycle, valve 1324 is
opened and valve 1326 is closed. Compressor 1312 is in operation,
while pump 1326 is turned off. Thus, refrigerant flows from
compressor 1312 through outside coil 1314 and metering device 1320,
and then flows through open valve 1322 to reach thermal storage
device 1318. After absorbing heat from the phase change materials
contained within thermal storage device 1318 (and thus "charging"
thermal storage thermal storage device with "coolness"), primarily
gaseous refrigerant flows through optional separator 1330 and
returns to compressor 1312.
For operation of system 1310 in the discharging cycle, refrigerant
can flow either in the bypass line alone or simultaneously in the
bypass line and in the main flow loop. To initiate flow in the
bypass line, valves 1322 and 1324 are both closed. Compressor 1312
is turned off, and pump 1326 is turned on. Thus, pump 1326 pumps
refrigerant through inside coil 1316, where the refrigerant picks
up heat and discharges "coolness" to the space to be conditioned.
The primarily gaseous refrigerant then passes through optional
liquid separator 1330 and returns to thermal storage device
1318.
To initiate flow in the main flow loop in the discharging cycle
while maintaining flow in the bypass line, compressor 1312 is
turned on and valve 1324 is opened. Valve 1322 remains open and
pump 1326 remains on. Thus, refrigerant flows from compressor 1312
through outside coil 1314, metering device 1320, valve 1324, and
inside coil 1316 before returning to compressor 1312 (optionally
passing through liquid separator 1330). At the same time,
refrigerant circulates in the bypass line from pump 1326 to inside
coil 1316 through liquid separator 1330 and to thermal storage
device 1318 (thus flowing in the bypass line in a counterclockwise
direction). As previously noted, this may allow the compressor
capacity to be reduced significantly with no loss in
performance.
Yet another embodiment of the claimed invention is illustrated in
FIG. 14. System 1410 shown in FIG. 14 may be operated as a heat
pump. System 1410 includes a compressor 1412, outside coil 141,
inside coil 1416, and thermal storage device 1418. System 1410
further includes a metering device 1420, three valves 1422, 1424,
and 1426, and a reversing valve 1428. It will be recognized from
the description below that valve 1426 is optional. A refrigerant
pump 1430 is also provided, and a controller 1444 is optionally
provided.
For operation of system 1410 in a conventional cycle, valve 1424 is
open, while valves 1422 and 1426 are closed. Compressor 1412 is
turned on, while pump 1430 is turned off. Refrigerant thus flows
from compressor 1412 through outside coil 141, and through metering
device 1420. Because valve 1422 is closed and valve 1424 is open,
refrigerant flows through valve 1424 to reach inside coil 1416.
Because valve 1426 is also closed, refrigerant exiting inside coil
1416 flows through line 1436 and through reversing valve 1428. It
can then flow through optional liquid separator 1440 to reach
compressor 1412.
For operation of system 1410 as a heat pump in a charging cycle,
valves 1426 and 1422 are open, while valve 1424 is closed.
Compressor 1412 is turned on, and pump 1430 is turned off. Thus,
refrigerant flows from compressor 1412 through reversing valve 1428
to line 1436. Because valve 1426 is open and valve 1424 is closed,
refrigerant flows through valve 1426 to reach thermal storage
device 1418, releasing heat to the phase change materials contained
within device 1418. Upon exiting thermal storage device 1418,
refrigerant passes through open valve 1422 and passes through
metering device 1420 to reach outside coil 1414. From there,
refrigerant returns to compressor 1412 by way of reversing valve
1428, passing through optional liquid separator 1440.
For operation of system 1410 as a heat pump in the discharging
cycle, valve 1426 is open, wile valves 1424 and 1422 are closed.
Compressor 1312 is turned off, while pump 1430 is turned on.
Auxiliary heater 1438 may be turned on.
Thus, in this configuration, refrigerant is pumped by pump 1430
through thermal storage device 1418, open valve 1426, junction
1432, and inside coil 1416 (thus flowing in a clockwise direction
in the bypass line). There, the refrigerant liquefies and flows
through junction 1442 to pump 1430. Because valve 1422 is closed,
the refrigerant continues to circulate in the bypass line,
returning to thermal storage device 1418 to absorb heat from the
phase change materials and from auxiliary heater 1438.
To initiate flow in the main flow loop in the discharging cycle
while maintaining flow in the bypass line, valve 1422 is closed,
but valves 1424 and 1426 are opened. Compressor 1412 and pump 1430
are both turned on. Thus, refrigerant flows from compressor 1412
through reversing valve 1428 and through line 1436 to junction
1432. There, the refrigerant joins the bypass flow (i.e. the flow
reaching junction 1432 by way of thermal storage device 1418 and
open valve 1426). The combined refrigerant flow passes through
inside coil 1416, then flows to junction 1442. At junction 1442, a
portion of the refrigerant returns to the bypass line, passing
through pump 1430 and thermal storage device 1418 as previously
described. The remainder of the refrigerant flows through junction
1442 in the main flow loop, passing through metering device 1420
and through outside coil 141, ultimately returning to compressor
1412 by way of reversing valve 1428 and optional liquid separator
1440.
As previously noted, system 1410 can also operate as an air
conditioner or refrigeration system. In the charging cycle, valves
1422 and 1426 are opened, while valve 1424 is closed. Compressor
1412 is on, and pump 1430 is off. Refrigerant flows from compressor
1412 through reversing valve 1428 to outside coil 1414. Refrigerant
then passes through metering device 1420 and through open valve
1422 to thermal storage device 1418, absorbing heat from the phase
change materials therein (i.e., charging the phase change materials
with "coolness"). From there, refrigerant flows through open valve
1426 and returns to compressor 1412.
For operation of system 1410 as an air conditioner or refrigeration
system in a discharging cycle, valve 1426 is opened, and valves
1422 and 1424 are closed to initiate flow in the bypass line.
Compressor 1412 is off, and pump 1430 is on. Refrigerant is pumped
by pump 1430 through inside coil 1416, through open valve 1426, and
through thermal storage device 1418 (thus flowing in a
counterclockwise direction). Because valve 1422 is closed,
refrigerant must return to pump 1430 and continue to circulate in
the bypass line.
To initiate flow in the main flow loop in the discharging cycle
while maintaining flow in the bypass line, valves 1424 and 1426 are
both opened, and valve 1422 is closed. Both pump 1430 and
compressor 1412 are turned on. Thus, refrigerant flows from
compressor 1412 through reversing valve, then through outside coil
141, and through metering device 1420, subsequently passing through
open valve 1424 and reaching junction 1442. At the same time,
refrigerant is flowing in the bypass line as described above. Thus,
the combined refrigerant flow at junction 1442 flows through inside
coil 1416, evaporates, then passes to junction 1432. There, a
portion of the refrigerant returns to the bypass line, passing
through valve 1426 to reach thermal storage device 1418, where the
refrigerant liquefies and then flows to pump 1430 as previously
described. The remainder of the refrigerant continues flowing in
the main flow loop, passing through junction 1432 and returning to
compressor 1412 by way of reversing valve 1428.
Another embodiment of the present invention is illustrated in FIG.
15. System 1510 includes a compressor 1512, outside coil 1514,
inside coil 1516, and thermal storage device 1518. System 1510
further includes metering devices 1546, 1548, three valves 1522,
1524, and 1526, and a reversing valve 1528. A refrigerant pump 1530
is also provided. A controller 1544, a liquid separator 1540, and a
heating coil 1538 extending through thermal storage device 1518 are
all optional.
For operation of system 1510 in a conventional cycle, valve 1524 is
open, while valves 1522 and 1526 are closed. Compressor 1524 is
turned on, while pump 1530 is turned off. Refrigerant thus flows
from compressor 1512 through outside coil 1514, through opened
valve 1524, and through metering device 1520 to reach inside coil
1516. Refrigerant exiting inside coil 1516 flows through line 1536
and through reversing valve 1528. It can then flow through optional
liquid separator 1540 to reach compressor 1512.
For operation of system 1510 as an air conditioner in the charging
cycle, valve 1526 is opened, while valves 1522 and 1524 are closed.
Compressor 1512 is on, and pump 1530 is off. Refrigerant flows from
compressor 1512 through reversing valve 1528 to outside coil 1514.
Refrigerant then passes through metering device 1548 and through
thermal storage device 1518, absorbing heat from the phase change
materials therein. From there, refrigerant flows through open valve
1526 and returns to compressor 1512.
For operation of system 1510 in the discharging cycle, valves 1524
and 1526 are closed while valve 1522 is opened. Gaseous refrigerant
from compressor 1512 enters outside coil 1514 and liquefies, and
the mainly liquid refrigerant flows through junction 1550 through
opened valve 1522. Refrigerant subsequently passes through junction
1560 to reach thermal storage device 1518. The mainly liquid
refrigerant becomes subcooled in thermal storage device 1518 and
exits by way of line 1554.
Because pump 1530 is still turned off, the refrigerant flows
through metering device 1546 and passes through junction 1542 to
reach inside coil 1516, where it evaporates. Superheated vapor
refrigerant exiting inside coil 1516 flows through junction 1532
and returns to compressor 1512 by way of reversing valve 1528.
After system 1510 is operated in this configuration for a
predetermined period of time, liquid refrigerant fills the inlet
line to pump 1530. Advantageously, only at this point is pump 1530
turned on, reducing the possibility that pump 1530 will be started
when the inlet line is empty of refrigerant. At this point, valve
1522 is closed and valve 1526 is opened. System 1510 can then be
operated in the discharging cycles in the same fashion as
previously described for FIG. 14.
Another embodiment of the invention is illustrated in FIG. 16. The
system 1610 of FIG. 16, which can provide refrigeration to a space,
includes a main refrigeration loop including compressor 1612,
condenser 1614, first optional liquid refrigerant receiver 1615,
first metering device 1616 with a temperature sensor 1617 having a
setting for superheating, thermal storage device 1618 including a
thermal storage medium, second optional liquid refrigerant receiver
1651, second metering device 1620 with a temperature sensor 1621
having a setting for superheating, and evaporator 1622,
interconnected in series by main refrigeration line 1624. System
1610 also includes first bypass line 1626 containing first bypass
valve 1628 and a third metering device 1629 with a temperature
sensor 1649 having a setting for supercooling. First bypass line
1626 is connected to main refrigeration line 1624 at locations so
as to selectively bypass first metering device 1616 depending upon
the open or closed condition of first bypass valve 1628. Those
skilled in the art will readily understand and appreciate that
instead of two metering devices, 1616 with setting for superheating
and 1629 with setting for supercooling, one device with variable
setting may be used, for example an Ana-Loid, Parker Hannatin's
proportional solenoid valve.
System 1610 further includes second optional liquid receiver 1651
located after the thermal storage device 1618, second bypass line
1630 connected to main line 1624 at locations so as to bypass
second metering device 1620 and evaporator 1622. Second bypass line
1630 includes second bypass valve 1632 which can be opened to cause
such bypass, or closed to prevent such bypass. A reverse flow, hot
gas defrost loop is also provided, and includes third bypass line
1634 connected on one end to main line 1624 immediately to the high
pressure side of compressor 1612, and at the other end at a
location intermediate evaporator 1622 and compressor 1612 as
illustrated. Third bypass valve 1636 is also provided in third
bypass line 1634. The hot gas defrost loop also includes fourth
bypass line 1638 connected to main line 1624 at a position
intermediate second metering device 1620 and evaporator 1622, and
at a position intermediate compressor 1612 and first metering
device 1616, preferably as illustrated in between condenser 1614
and optional receiver 1615, or otherwise between condenser 1614 and
first metering device 1616. Fourth bypass line 1638 also includes
fourth bypass valve 1640. To facilitate the defrost cycle, valves
1641 and 1642 are also provided in main line 1624, with valve 1642
at a position intermediate third bypass line 1634 and compressor
1612, and valve 1641 at a position intermediate third bypass line
1634 and condenser 1614. Fifth bypass line 1644 including valve
1646 is also provided and serves to selectively bypass thermal
storage device 1618 and first metering device 1616.
In the operation of system 1610 during a thermal storage charging
mode, bypass valves 1628, 1636, 1640 and 1646 are closed. After
exiting compressor 1612 gaseous refrigerant condenses in condenser
1614, passes through metering device 1616, and evaporates in
thermal storage device 1618 absorbing heat from the thermal storage
media, then passes through bypass line 1630 with valve 1632 in open
position refrigerant flows back to compressor 1612 whereafter the
cycle repeats.
In the operation of system 1610 during a refrigeration mode, bypass
valves 1632, 1636, 1640 and 1646 are closed. Compressed, gaseous
refrigerant exits compressor 1612 and is condensed substantially to
liquid in condenser 1614. This liquid refrigerant passes through
first bypass line 1626, through third metering device 1629 set for
supercooling, and into thermal storage device 1618. There, if the
thermal storage medium is charged with low temperature potential,
the liquid refrigerant in the metering device 1629 expands with
vapor phase (line 3--3', FIG. 21), which further is subjected to
low-temperature condensation (line 3'-4, FIG. 21). If the thermal
storage medium is not charged with negative thermal potential,
metering device 1629 is completely opened and the refrigerant
simply flows through the thermal storage, and then passes through
second metering device 1620 set for superheating and to evaporator
1622. The refrigerant is evaporated in evaporator 1622, collecting
heat from the environment surrounding evaporator 1622. The
refrigerant then flows to the suction side of compressor 1612
whereafter the cycle can be repeated.
In another arrangement for a refrigeration mode (conventional
cycle), valve 1646 is open and valve 1628 is closed, such that
refrigerant flows after condenser 1614 through fifth bypass line
1644 to second metering device 1620 and further through evaporator
1622 back to compressor 1612.
During a defrost cycle, bypass valves 1632, 1636 and 1640 are open,
and valves 1628, 1642 and 1646 are closed. Valve 1641 may be
opened, closed or partially opened in this arrangement. In this
manner, compressed, gaseous refrigerant exiting compressor 1612 is
directed in a reverse flow pattern, passing through third bypass
line 1634 and into evaporator 1622. If valve 1641 is completely or
partially opened, a portion of the refrigerant passes through
condenser 1614. Directing a portion of the refrigerant through
condenser 1614 may reduce thermal shock to evaporator 1622 when hot
refrigerant of the defrost cycle instantly replaces cold
refrigerant of refrigerant cycle. Thus, the reliability and
durability of refrigerant pipes in the system may be enhanced.
In the defrost mode, evaporator 1622 is actually acting as a full
or partial condenser, condensing the gaseous refrigerant which
imparts heat to the ice crystals built up on evaporator 1622
thereby melting the same. Correspondingly, the ice crystals
transfer negative thermal potential, or "coolness", to the
refrigerant. From evaporator 1622 the at least partially condensed
refrigerant passes through fourth bypass line 1638, through first
metering device 1616 and into thermal storage device 1618. There,
the refrigerant liberates negative thermal energy for collection in
thermal storage device 1618 for later use and is vaporized. After
exiting thermal storage device 1618, the gaseous refrigerant routes
through second bypass line 1630 and back to the suction side of
compressor 1612. The cycle can then be repeated for a predetermined
period of time necessary to adequately defrost evaporator 1622,
after which the system can be returned automatically to the
refrigeration mode described above. It will be appreciated that
system 1610, when operated in this fashion, provides a defrost
cycle in which negative thermal potential is collected at
evaporator 1622 and stored in thermal storage device 1618 to assist
in further low temperature condensing operations or otherwise in
the discharge of negative thermal potential from the thermal
storage device. Thus, the overall refrigeration capacity of the
system will be enhanced.
The low-temperature condensing mode of the system of FIG. 16 is
highly advantageous, providing increased capacity to the system.
Referring to FIG. 21, in the low-temperature condensing cycle, the
line 1-2 represents the function of the compressor as it compresses
gaseous refrigerant. Line 2-3 represents the function of the
conventional condenser, condensing the gaseous refrigerant
predominantly to liquid. Line 3-3' denotes the function of the
supercooling metering device, reducing the pressure of the
refrigerant, whereas line 3'-4 indicates the function of the low
temperature condenser (e.g. the thermal storage device) line 4-4'
depicts the function of a conventional superheating metering
device. Line 4-1 represents the function of the evaporator,
evaporating predominantly liquid-form refrigerant to gaseous
refrigerant. As illustrated in FIG. 21, an increase in cooling
capacity and efficiency can be achieved by the low-temperature
condensation cycle. Moreover, unlike subcooling, which is hard to
accomplish with a large thermal storage device (see FIGS. 22 and 23
and discussion above), realization of the low-temperature
condensing cycle requires only a metering device (i.e. a
thermostatic expansion valve with a sensing bulb set for
supercooling, a capillary tube, or an orifice). It will be
understood in this regard that FIG. 21 is illustrative in nature.
As is known, it is not uncommon to observe some small subcooling in
the condenser (line 2-3), in the thermal storage (line 3'-4), and
some superheating at the evaporator (line 4'-1). These and other
variations which will be recognized by those skilled in the art are
contemplated as falling within the spirit and scope of the present
invention.
Another embodiment of the invention is illustrated in FIG. 17. The
illustrated system 1710 can provide cooling to a food store
refrigeration rack or the like. System 1710 includes a main
refrigeration loop including a bank of one or more compressors, in
the illustrated system including those numbered 1712, 1714, 1716
and 1718 connected in parallel, condenser 1720, a metering device
1722 set for supercooling, thermal storage device 1724 including
first internal thermal exchange coil 1726, metering device 1728 set
for superheating, and evaporator (evaporators) 1730, connected by
main refrigeration line 1732. System 1710 also includes a thermal
storage charge loop which includes metering device 1734 set for
superheating, second internal coil 1736 extending through thermal
storage device 1724, and valve 1738, all connected by thermal
storage charge line 1740 which in turn is connected to main line
1732 so as to direct liquefied refrigerant exiting condenser 1720
through the thermal storage charge loop and directly back into the
suction side of the chosen compressor or compressors of the
compressor bank (thereby bypassing other components of the main
refrigeration loop discussed above).
System 1710 further includes a thermal storage bypass loop
including thermal storage bypass line 1742 for conventional
operation, which connects to main refrigeration line 1732 so as to
cause refrigerant to bypass metering device 1722 and thermal
storage device 1724, but otherwise proceed through the components
of the main refrigeration loop. Thermal storage bypass valve 1744
is located in thermal storage bypass line 1742.
To conduct a charging mode using compressor 1712 as discussed
below, valve 1746 is provided isolating the thermal storage charge
loop from all compressors but 1712. To eliminate unwanted
discharging of thermal storage negative potential, valve 1748 is
located in main refrigeration line 1732 at a position intermediate
metering device 1722 and thermal storage device 1724.
As discussed above in connection with system 1610 of FIG. 16, an
optional liquid refrigerant receiver after condenser 1720 and/or an
optional liquid refrigerant receiver after thermal storage device
1724 may be provided. Metering devices 1722, 1734 and 1728 may be
thermostatic expansion valves, or electronically driven expansion
valves, or orifices, or capillary tubes with device 1734 having
conventional superheating set to achieve full evaporation of
refrigerant in coil 1736 of thermal storage device 1724 in the
charging mode, device 1728 having a conventional superheating
setting to achieve full evaporation of refrigerant in evaporator
1730, and device 1722 having a supercooling setting to achieve full
condensation of the refrigerant in coil 1726 of thermal storage
1724 during low-temperature condensing and the thermal storage
discharging mode.
In operation in a low-temperature condensation cycle, to utilize
negative thermal storage capacity, valves 1738 and 1744 are closed,
and valves 1746 and 1748 are open. In this manner, refrigerant
passes through the main refrigeration loop and generally functions
as discussed above in connection with system 1610 of FIG. 16.
In a mode for charging thermal storage device 1724 and
simultaneously running a refrigeration cycle, valves 1746 and 1748
are closed, valves 1738 and 1744 are open, and compressors 1712,
1714, 1716 and 1718 are energized (any one of compressors 1714,
1716 and 1718 can of course be stopped so long as the rest supply
the system with sufficient refrigeration capacity). In this
fashion, compressed, gaseous refrigerant exiting compressor 1712 is
liquefied in condenser 1720, and then a portion of the refrigerant
passes through metering device 1734 and into thermal exchange coil
1736. The refrigerant is vaporized in coil 1736 as its negative
thermal potential is transferred to thermal storage device 1724.
The gaseous refrigerant exiting coil 1736 then passes back to the
suction side of compressor 1712, whereafter the cycle can be
repeated. During this period, another portion of the refrigerant
passes through open valve 1744 and line 1742 and proceeds to
metering device 1730 and further to evaporator 1730 supplying the
system with cooling capacity.
Also in system 1710 a thermal storage charging mode can be
conducted simultaneously with a low-temperature condensing mode. In
such an operation, valves 1746 and 1744 are closed, valves 1748 and
1738 are open, and compressors 1712, 1714, 1716 and 1718 are
energized. Refrigerant thus passes from the compressor bank to
condenser 1720. A portion of the liquefied refrigerant exiting
condenser 1720 then passes through the thermal storage charging
loop and a portion passes through the main refrigerant loop, both
as discussed in detail above. In this manner, thermal storage
device 1724 simultaneously is charged and serves as a
low-temperature condenser to increase cooling capacity of system
including compressors 1714, 1716 and 1718.
System 1710 can also be operated in a conventional mode (i.e.
without low-temperature condensation by or charging of the thermal
storage device). In this mode valves 1738 and 1748 are closed,
valves 1744 and 1746 are open, and all or part of compressors 1712,
1714, 1716 and 1718 are energized. Thus, compressed refrigerant gas
passes from the compressor bank through condenser 1720 where it is
liquefied, through metering device 1728, through evaporator 1730
where it is vaporized, and back to the suction side of the
compressor bank. A conventional refrigeration cycle is thereby
accomplished.
FIG. 18 illustrates another embodiment of a refrigeration system of
the invention. Generally, system 1810 illustrated in FIG. 18 is
similar to system 1710 of FIG. 17, except that a compressor from a
second, associated refrigeration or air conditioning system is used
to charge the thermal storage device. Thus, system 1810 includes a
first refrigeration system 1810A which includes components
corresponding to those in the main refrigeration loop and thermal
storage bypass loop in system 1710 of FIG. 17, including optional
liquid refrigerant receivers. These components in FIG. 18 are given
numbers which correspond to those analogous components in FIG. 17
except in FIG. 18 the numbers are in the 1800's series instead of
the 1700's, e.g. 1712 corresponds with 1812, etc. For additional
detail as to each illustrated component, reference can be made to
the discussion in connection with FIG. 17 above.
System 1810 also includes a second refrigeration system 1810B which
can for example be an adjacent food refrigeration rack or air
conditioning system of the building having one or more high
temperature refrigeration compressors. System 1810B includes a
conventional refrigeration loop including a bank of compressors
1852, 1854, and 1856 arranged in parallel, condenser 1858, metering
device 1860, and evaporator 1862, all connected in series by main
refrigeration line 1864. System 1810B further includes a thermal
storage device charging loop with metering device 1866 set for
superheating, thermal exchange coil 1868 passing internal of
thermal storage device 1824, and valve 1870. System 1810B includes
valve 1872 which when closed isolates a single compressor 1852 or
several compressors of the compressor bank from evaporator 1862,
and as discussed further below can be used in a mode for charging
thermal storage device 1824.
Similar to system 1710, system 1810 can be operated in charging,
low-temperature condensing, combined charging/low-temperature
condensing, and conventional modes. In a charging only mode, valves
1844 and 1870 are open, valves 1848 and 1872 are closed, and
compressor 1852 of system 1810B is energized. In this manner,
refrigerant in system 1810A will bypass thermal storage device 1824
and thus system 1810 will operate in a conventional mode (without
low-temperature condensing). At the same time, in system 1810B,
compressed refrigerant gas from compressor 1852 will be liquefied
in condenser 1858 and then passed through metering device 1866 and
into thermal exchange coil 1868. In coil 1868 the refrigerant will
transfer negative thermal potential to thermal storage device 1824
and be vaporized. Refrigerant gas then exiting thermal exchange
coil 1868 will than pass to the suction side of compressor 1852,
and the cycle can be repeated to further charge thermal storage
device 1824 with negative thermal potential. The rest of
compressors 1854 and 1856 of system 1810B may also operate in
conventional mode.
In a simultaneous charging/low-temperature condensing mode, valves
1848 and 1870 are open, valves 1844 and 1872 are closed, and
compressor 1852 is energized. As a result, refrigerant in system
1810A is routed through thermal storage device 1824 and the system
operates in a low-temperature condensing mode simultaneously
storing excessive negative capacity of the system 1810B in the
thermal storage device. Part of the system 1810B, simultaneously
operates in a conventional mode as described above.
In a low-temperature condensing only mode of system 1810, valves
1844 and 1870 are closed, valves 1848 and 1872 are open, and
compressor 1852 is optionally energized. In this fashion, the whole
system 1810B will be operating in its normal refrigeration cycle
(with no charging of thermal storage device 1824), and system 1810A
will be operating in a cycle with low-temperature condensation (see
FIG. 21).
The operation of system 1810 in a conventional mode involves
closing valves 1848 and 1870, opening valves 1844 and 1872, and
optionally energizing any compressor of the systems 1810A and
1810B. Both systems 1810A and 1810B will thereby operate in a
conventional mode, isolated from thermal storage device 1824.
FIG. 19 is a diagrammatic view of another embodiment of a
refrigeration system of the invention. Generally, the illustrated
system 1910 includes a refrigeration system 1910A including
components similar to those of system 1710 previously described,
and which are correspondingly numbered as in FIG. 18. In addition,
system 1910A includes a reverse flow, hot gas defrost loop such as
that described in FIG. 16. Thus, bypass line 1950 is connected on
one end to main line 1932 immediately to the high pressure side of
the compressor bank, and at the other end at a location
intermediate evaporator 1930 and the compressor bank as
illustrated. Third bypass valve 1952 is also provided in third
bypass line 1950. Valve 1951 may also be provided to selectively
stop refrigerant flow through condenser 1920. The hot gas defrost
loop also includes bypass line 1954 connected to main line 1932 at
a position intermediate first metering device 1928 and evaporator
1930, and to the thermal storage device at a position intermediate
the second metering device 1922 and thermal storage coil 1926.
Bypass line 1954 also includes bypass valve 1956 and third metering
device 1927 set for superheating. Bypass line 1959 is also
provided, and includes valve 1961. To facilitate the defrost cycle,
valve 1958 is also provided in main line 1932 at a position
intermediate bypass line 1950 and the suction side of the
compressor bank, as illustrated. System 1910A further includes
bypass line 1960 connected to main line 1932 at locations so as to
bypass metering device 1928 and evaporator 1930. Bypass line 1960
includes bypass valve 1962 which can be opened to cause such
bypass, or closed to prevent such bypass.
System 1910 also includes external charging loop 1910B for charging
thermal storage device 1924. External charging loop includes
compressor 1964, condenser 1966, metering device 1968, thermal
exchange coil 1970 passing internal of thermal storage device 1924,
all connected in series by external charging line 1972. Optional
liquid refrigerant receiver 1971 may also be provided.
System 1910, like systems 1710 and 1810, can be operated in
charging, combined charging/low-temperature condensing and
conventional modes In a conventional mode with charging of the
thermal storage, valves 1944, 1951, and 1958 are open, valves 1948,
1952, 1956, 1961 and 1962 are closed, and compressor 1964 is
energized. In this fashion, external charging loop 1910B will
charge thermal storage device 1924 with negative thermal potential,
while system 1910A simultaneously operates in a conventional
cycle.
In a combined charging/low-temperature condensing mode, valves
1948, 1951, and 1958 are open, valves 1944, 1952, 1956, 1961 and
1962 are closed, and compressor 1964 is energized. Thus, external
charging loop 1910B will charge thermal storage device 1924 with
negative thermal potential, while system 1910A operates in a cycle
with low-temperature condensing.
A low-temperature condensing only mode can be achieved if
compressor 1964 is off. As in prior discussed systems, this mode
can be initiated when thermal storage device 1924 is adequately
charged with negative thermal potential for the low-temperature
condensation.
System 1910 can be operated in a conventional mode with valves
1948, 1952, 1956, 1961, and 1962 closed, valves 1944, 1951, and
1958 open, and compressor 1964 off.
System 1910 can also operate in a reversed flow, hot gas defrost
cycle, wherein negative thermal potential from ice-laden evaporator
1930 is collected and delivered to thermal storage device 1924. In
this cycle, valves 1952, 1956 and 1962 are open, and valves 1944,
1948, 1958, and 1961 are closed. Thus, hot gaseous refrigerant
exiting the compressor bank will pass through line 1950 and into
evaporator 1930. Negative thermal potential will there be
transferred to the refrigerant, at least partially condensing the
same and causing ice crystals on evaporator 1930 to melt.
Refrigerant exiting evaporator 1930 will pass through line 1954
with metering device 1927 and into coil 1926 within thermal storage
device 1924. Refrigerant in coil 1926 will be vaporized and
transfer negative potential to thermal storage device 1924.
Refrigerant then exiting thermal storage device 1924 will pass
through line 1960 and return to the suction side of the compressor
bank. Valve 1951 may be closed, opened or partially opened to
reduce thermal shock in the coil of evaporator 1930. The cycle can
then be repeated for a duration sufficient to defrost the
evaporator. During such a defrost cycle, compressor 1964 of
external charge loop 1910B can be on or off, depending on whether
external charging of thermal storage device 1924 during the defrost
cycle is desired. Thermal storage 1924 may also be charged by one
or more of compressors 1912, 1914, 1916 and 1918 of the loop in
1910A. During this charge operation, valves 1951, 1961, and 1962
are open, and valves 1944, 1948, 1952, 1956 and 1958 are closed.
Liquid refrigerant exiting condenser 1920 passes through bypass
line 1959, expands in second metering device 1927, evaporates in
coil 1926 providing the thermal storage device 1924 with negative
thermal potential, and further flows to bypass line 1960 back to
the compressor bank. In this arrangement the loop 1910B is
optional.
Referring now to FIG. 20, shown is a diagrammatic view of another
embodiment of a refrigeration system of the invention. The
illustrated system 2010 is similar to that illustrated in FIG. 17
except only a single coil traverses the thermal storage device.
Thus, it is not possible to simultaneously run thermal storage
charging and refrigeration modes in system 2010.
More particularly, system 2010 includes a main refrigerant loop
having a bank of one or more compressors, in the illustrated system
including those numbered 2012, 2014, 2016 and 2018 connected in
parallel, condenser 2020, metering device 2022 set for
supercooling, thermal storage device 2024 having thermal exchange
coil 2026 internal thereof, metering device 2028 set for
superheating, and evaporator 2030, all connected in series via main
refrigerant line 2032. System 2010 also includes bypass line 2034
with valve 2033 connected to main line 2032 so as to cause
refrigerant exiting condenser 2020 to bypass main refrigerant line
2032, and metering device 2022, and pass into metering device 2036
set for superheating and further to thermal exchange coil 2026.
Bypass line 2038 is also provided connected to main line 2032 on
each side of thermal storage device 2024 so as to allow refrigerant
to selectively bypass thermal storage device 2024 for a
conventional refrigeration cycle as discussed below. Bypass line
2038 includes valve 2040 to facilitate this purpose.
Bypass line 2042 is also provided and is connected at one end of
thermal exchange coil 2026 and at the other end to the suction side
of the compressor bank. Bypass line 2042 includes bypass valve 2044
located therein, and serves to allow refrigerant to selectively
bypass metering device 2028 and evaporator 2030 in the main
refrigeration loop.
Valve 2046 is positioned in main refrigeration line 2032 at a
position intermediate condenser 2020 and metering device 2022 and
facilitates the selective conduct of a conventional cycle as
discussed further below. Valve 2048 is positioned in main
refrigeration line 2032 at a position intermediate thermal exchange
coil 2026 and first metering device 2028 and facilitates the
selective conduct of a charging cycle as discussed further below.
Valve 2050 is provided in the compressor bank to isolate compressor
2012 or compressors of the compressor bank for a charging mode as
discussed below.
System 2010 can be operated in charging, refrigeration with
low-temperature condensing, and conventional refrigeration modes.
In a conventional mode with charge of the thermal storage, valves
2033, 2040, 2044 are open, valves 2046, 2048, and 2050 are closed,
and compressor 2012 is energized. Thermal storage device 2024 is
thereby charged as generally discussed in connection with systems
1710-1910 above. During refrigeration with low-temperature
condensing, valves 2046, 2048, and 2050 are open, valves 2033,
2040, and 2044 are closed, and compressor 2012 can optionally be
energized. And, during a conventional cycle, valves 2040, 2048 and
2050 are open, valves 2033, 2044 and 2046 are closed, and
compressor 2012 can optionally be energized. In this mode, valve
2048 is opened in order to use refrigerant which might otherwise be
trapped in thermal exchange coil 2026.
It will be understood that system 2010, as well as the other
systems disclosed herein, can all be equipped for hot gas defrost
systems as discussed in connection with FIGS. 16 and 19. Such
systems advantageously provide efficient defrost cycles while also
delivering negative thermal potential to thermal storage. In
addition, receivers may be optionally be included at appropriate
locations, e.g. corresponding to the locations in the systems
discussed above. In addition, it will be understood that the
inventive cycles with low-temperature condensing can also be
operated without a thermal storage device, using conventional
condensing devices in conjunction with means for cooling after such
devices. For example, a metering device with setting for
supercooling and a low-temperature condenser can be installed after
a conventional condenser in the main refrigeration loop, and this
low-temperature condenser can be associated with the cooling
capacity of a second refrigeration loop (mechanical subcooling),
wherein no thermal storage need take place but rather the
mechanical transfer of negative thermal potential to the
low-temperature condenser may be utilized.
Although the invention has been described in detail with reference
to certain preferred embodiments, variations and modifications
exist within the spirit and scope of the invention as defined in
the following claims.
* * * * *